| Message ID | 20210701041552.112072-2-srikar@linux.vnet.ibm.com (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
| Series | Skip numa distance for offline nodes | expand |
| Related | show |
| Context | Check | Description |
|---|---|---|
| snowpatch_ozlabs/apply_patch | success | Successfully applied on branch powerpc/merge (086d9878e1092e7e69a69676ee9ec792690abb1d) |
| snowpatch_ozlabs/checkpatch | warning | total: 0 errors, 0 warnings, 1 checks, 41 lines checked |
| snowpatch_ozlabs/needsstable | success | Patch has no Fixes tags |
On 01/07/21 09:45, Srikar Dronamraju wrote: > @@ -1891,12 +1894,30 @@ void sched_init_numa(void) > void sched_domains_numa_masks_set(unsigned int cpu) > { > int node = cpu_to_node(cpu); > - int i, j; > + int i, j, empty; > > + empty = cpumask_empty(sched_domains_numa_masks[0][node]); > for (i = 0; i < sched_domains_numa_levels; i++) { > for (j = 0; j < nr_node_ids; j++) { > - if (node_distance(j, node) <= sched_domains_numa_distance[i]) > + if (!node_online(j)) > + continue; > + > + if (node_distance(j, node) <= sched_domains_numa_distance[i]) { > cpumask_set_cpu(cpu, sched_domains_numa_masks[i][j]); > + > + /* > + * We skip updating numa_masks for offline > + * nodes. However now that the node is > + * finally online, CPUs that were added > + * earlier, should now be accommodated into > + * newly oneline node's numa mask. > + */ > + if (node != j && empty) { > + cpumask_or(sched_domains_numa_masks[i][node], > + sched_domains_numa_masks[i][node], > + sched_domains_numa_masks[0][j]); > + } > + } Hmph, so we're playing games with masks of offline nodes - is that really necessary? Your modification of sched_init_numa() still scans all of the nodes (regardless of their online status) to build the distance map, and that is never updated (sched_init_numa() is pretty much an __init function). So AFAICT this is all to cope with topology_span_sane() not applying 'cpu_map' to its masks. That seemed fine to me back when I wrote it, but in light of having bogus distance values for offline nodes, not so much... What about the below instead? --- diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c index b77ad49dc14f..c2d9caad4aa6 100644 --- a/kernel/sched/topology.c +++ b/kernel/sched/topology.c @@ -2075,6 +2075,7 @@ static struct sched_domain *build_sched_domain(struct sched_domain_topology_leve static bool topology_span_sane(struct sched_domain_topology_level *tl, const struct cpumask *cpu_map, int cpu) { + struct cpumask *intersect = sched_domains_tmpmask; int i; /* NUMA levels are allowed to overlap */ @@ -2090,14 +2091,17 @@ static bool topology_span_sane(struct sched_domain_topology_level *tl, for_each_cpu(i, cpu_map) { if (i == cpu) continue; + /* - * We should 'and' all those masks with 'cpu_map' to exactly - * match the topology we're about to build, but that can only - * remove CPUs, which only lessens our ability to detect - * overlaps + * We shouldn't have to bother with cpu_map here, unfortunately + * some architectures (powerpc says hello) have to deal with + * offline NUMA nodes reporting bogus distance values. This can + * lead to funky NODE domain spans, but since those are offline + * we can mask them out. */ + cpumask_and(intersect, tl->mask(cpu), tl->mask(i)); if (!cpumask_equal(tl->mask(cpu), tl->mask(i)) && - cpumask_intersects(tl->mask(cpu), tl->mask(i))) + cpumask_intersects(intersect, cpu_map)) return false; }
Hi Valentin, > On 01/07/21 09:45, Srikar Dronamraju wrote: > > @@ -1891,12 +1894,30 @@ void sched_init_numa(void) > > void sched_domains_numa_masks_set(unsigned int cpu) > > { > > Hmph, so we're playing games with masks of offline nodes - is that really > necessary? Your modification of sched_init_numa() still scans all of the > nodes (regardless of their online status) to build the distance map, and > that is never updated (sched_init_numa() is pretty much an __init > function). > > So AFAICT this is all to cope with topology_span_sane() not applying > 'cpu_map' to its masks. That seemed fine to me back when I wrote it, but in > light of having bogus distance values for offline nodes, not so much... > > What about the below instead? > > --- > diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c > index b77ad49dc14f..c2d9caad4aa6 100644 > --- a/kernel/sched/topology.c > +++ b/kernel/sched/topology.c > @@ -2075,6 +2075,7 @@ static struct sched_domain *build_sched_domain(struct sched_domain_topology_leve > static bool topology_span_sane(struct sched_domain_topology_level *tl, > const struct cpumask *cpu_map, int cpu) > { > + struct cpumask *intersect = sched_domains_tmpmask; > int i; > > /* NUMA levels are allowed to overlap */ > @@ -2090,14 +2091,17 @@ static bool topology_span_sane(struct sched_domain_topology_level *tl, > for_each_cpu(i, cpu_map) { > if (i == cpu) > continue; > + > /* > - * We should 'and' all those masks with 'cpu_map' to exactly > - * match the topology we're about to build, but that can only > - * remove CPUs, which only lessens our ability to detect > - * overlaps > + * We shouldn't have to bother with cpu_map here, unfortunately > + * some architectures (powerpc says hello) have to deal with > + * offline NUMA nodes reporting bogus distance values. This can > + * lead to funky NODE domain spans, but since those are offline > + * we can mask them out. > */ > + cpumask_and(intersect, tl->mask(cpu), tl->mask(i)); > if (!cpumask_equal(tl->mask(cpu), tl->mask(i)) && > - cpumask_intersects(tl->mask(cpu), tl->mask(i))) > + cpumask_intersects(intersect, cpu_map)) > return false; > } > Unfortunately this is not helping. I tried this patch alone and also with 2/2 patch of this series where we update/fill fake topology numbers. However both cases are still failing.
On 12/07/21 18:18, Srikar Dronamraju wrote: > Hi Valentin, > >> On 01/07/21 09:45, Srikar Dronamraju wrote: >> > @@ -1891,12 +1894,30 @@ void sched_init_numa(void) >> > void sched_domains_numa_masks_set(unsigned int cpu) >> > { >> >> Hmph, so we're playing games with masks of offline nodes - is that really >> necessary? Your modification of sched_init_numa() still scans all of the >> nodes (regardless of their online status) to build the distance map, and >> that is never updated (sched_init_numa() is pretty much an __init >> function). >> >> So AFAICT this is all to cope with topology_span_sane() not applying >> 'cpu_map' to its masks. That seemed fine to me back when I wrote it, but in >> light of having bogus distance values for offline nodes, not so much... >> >> What about the below instead? >> >> --- >> diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c >> index b77ad49dc14f..c2d9caad4aa6 100644 >> --- a/kernel/sched/topology.c >> +++ b/kernel/sched/topology.c >> @@ -2075,6 +2075,7 @@ static struct sched_domain *build_sched_domain(struct sched_domain_topology_leve >> static bool topology_span_sane(struct sched_domain_topology_level *tl, >> const struct cpumask *cpu_map, int cpu) >> { >> + struct cpumask *intersect = sched_domains_tmpmask; >> int i; >> >> /* NUMA levels are allowed to overlap */ >> @@ -2090,14 +2091,17 @@ static bool topology_span_sane(struct sched_domain_topology_level *tl, >> for_each_cpu(i, cpu_map) { >> if (i == cpu) >> continue; >> + >> /* >> - * We should 'and' all those masks with 'cpu_map' to exactly >> - * match the topology we're about to build, but that can only >> - * remove CPUs, which only lessens our ability to detect >> - * overlaps >> + * We shouldn't have to bother with cpu_map here, unfortunately >> + * some architectures (powerpc says hello) have to deal with >> + * offline NUMA nodes reporting bogus distance values. This can >> + * lead to funky NODE domain spans, but since those are offline >> + * we can mask them out. >> */ >> + cpumask_and(intersect, tl->mask(cpu), tl->mask(i)); >> if (!cpumask_equal(tl->mask(cpu), tl->mask(i)) && >> - cpumask_intersects(tl->mask(cpu), tl->mask(i))) >> + cpumask_intersects(intersect, cpu_map)) >> return false; >> } >> > > Unfortunately this is not helping. > I tried this patch alone and also with 2/2 patch of this series where > we update/fill fake topology numbers. However both cases are still failing. > Thanks for testing it. Now, let's take examples from your cover letter: node distances: node 0 1 2 3 4 5 6 7 0: 10 20 40 40 40 40 40 40 1: 20 10 40 40 40 40 40 40 2: 40 40 10 20 40 40 40 40 3: 40 40 20 10 40 40 40 40 4: 40 40 40 40 10 20 40 40 5: 40 40 40 40 20 10 40 40 6: 40 40 40 40 40 40 10 20 7: 40 40 40 40 40 40 20 10 But the system boots with just nodes 0 and 1, thus only this distance matrix is valid: node 0 1 0: 10 20 1: 20 10 topology_span_sane() is going to use tl->mask(cpu), and as you reported the NODE topology level should cause issues. Let's assume all offline nodes say they're 10 distance away from everyone else, and that we have one CPU per node. This would give us: NODE->mask(0) == 0,2-7 NODE->mask(1) == 1-7 The intersection is 2-7, we'll trigger the WARN_ON(). Now, with the above snippet, we'll check if that intersection covers any online CPU. For sched_init_domains(), cpu_map is cpu_active_mask, so we'd end up with an empty intersection and we shouldn't warn - that's the theory at least. Looking at sd_numa_mask(), I think there's a bug with topology_span_sane(): it doesn't run in the right place wrt where sched_domains_curr_level is updated. Could you try the below on top of the previous snippet? If that doesn't help, could you share the node distances / topology masks that lead to the WARN_ON()? Thanks. --- diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c index b77ad49dc14f..cda69dfa4065 100644 --- a/kernel/sched/topology.c +++ b/kernel/sched/topology.c @@ -1516,13 +1516,6 @@ sd_init(struct sched_domain_topology_level *tl, int sd_id, sd_weight, sd_flags = 0; struct cpumask *sd_span; -#ifdef CONFIG_NUMA - /* - * Ugly hack to pass state to sd_numa_mask()... - */ - sched_domains_curr_level = tl->numa_level; -#endif - sd_weight = cpumask_weight(tl->mask(cpu)); if (tl->sd_flags) @@ -2131,7 +2124,12 @@ build_sched_domains(const struct cpumask *cpu_map, struct sched_domain_attr *att sd = NULL; for_each_sd_topology(tl) { - +#ifdef CONFIG_NUMA + /* + * Ugly hack to pass state to sd_numa_mask()... + */ + sched_domains_curr_level = tl->numa_level; +#endif if (WARN_ON(!topology_span_sane(tl, cpu_map, i))) goto error;
* Valentin Schneider <valentin.schneider@arm.com> [2021-07-13 17:32:14]: > On 12/07/21 18:18, Srikar Dronamraju wrote: > > Hi Valentin, > > > >> On 01/07/21 09:45, Srikar Dronamraju wrote: > >> > @@ -1891,12 +1894,30 @@ void sched_init_numa(void) > >> > void sched_domains_numa_masks_set(unsigned int cpu) > >> > { > > > > Unfortunately this is not helping. > > I tried this patch alone and also with 2/2 patch of this series where > > we update/fill fake topology numbers. However both cases are still failing. > > > > Thanks for testing it. > > > Now, let's take examples from your cover letter: > > node distances: > node 0 1 2 3 4 5 6 7 > 0: 10 20 40 40 40 40 40 40 > 1: 20 10 40 40 40 40 40 40 > 2: 40 40 10 20 40 40 40 40 > 3: 40 40 20 10 40 40 40 40 > 4: 40 40 40 40 10 20 40 40 > 5: 40 40 40 40 20 10 40 40 > 6: 40 40 40 40 40 40 10 20 > 7: 40 40 40 40 40 40 20 10 > > But the system boots with just nodes 0 and 1, thus only this distance > matrix is valid: > > node 0 1 > 0: 10 20 > 1: 20 10 > > topology_span_sane() is going to use tl->mask(cpu), and as you reported the > NODE topology level should cause issues. Let's assume all offline nodes say > they're 10 distance away from everyone else, and that we have one CPU per > node. This would give us: > No, All offline nodes would be at a distance of 10 from node 0 only. So here node distance of all offline nodes from node 1 would be 20. > NODE->mask(0) == 0,2-7 > NODE->mask(1) == 1-7 so NODE->mask(0) == 0,2-7 NODE->mask(1) should be 1 and NODE->mask(2-7) == 0,2-7 > > The intersection is 2-7, we'll trigger the WARN_ON(). > Now, with the above snippet, we'll check if that intersection covers any > online CPU. For sched_init_domains(), cpu_map is cpu_active_mask, so we'd > end up with an empty intersection and we shouldn't warn - that's the theory > at least. Now lets say we onlined CPU 3 and node 3 which was at a actual distance of 20 from node 0. (If we only consider online CPUs, and since scheduler masks like sched_domains_numa_masks arent updated with offline CPUs,) then NODE->mask(0) == 0 NODE->mask(1) == 1 NODE->mask(3) == 0,3 cpumask_and(intersect, tl->mask(cpu), tl->mask(i)); if (!cpumask_equal(tl->mask(cpu), tl->mask(i)) && cpumask_intersects(intersect, cpu_map)) cpu_map is 0,1,3 intersect is 0 From above NODE->mask(0) is !equal to NODE->mask(1) and cpumask_intersects(intersect, cpu_map) is also true. I picked Node 3 since if Node 1 is online, we would have faked distance for Node 2 to be at distance of 40. Any node from 3 to 7, we would have faced the same problem. > > Looking at sd_numa_mask(), I think there's a bug with topology_span_sane(): > it doesn't run in the right place wrt where sched_domains_curr_level is > updated. Could you try the below on top of the previous snippet? > > If that doesn't help, could you share the node distances / topology masks > that lead to the WARN_ON()? Thanks. > > --- > diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c > index b77ad49dc14f..cda69dfa4065 100644 > --- a/kernel/sched/topology.c > +++ b/kernel/sched/topology.c > @@ -1516,13 +1516,6 @@ sd_init(struct sched_domain_topology_level *tl, > int sd_id, sd_weight, sd_flags = 0; > struct cpumask *sd_span; > > -#ifdef CONFIG_NUMA > - /* > - * Ugly hack to pass state to sd_numa_mask()... > - */ > - sched_domains_curr_level = tl->numa_level; > -#endif > - > sd_weight = cpumask_weight(tl->mask(cpu)); > > if (tl->sd_flags) > @@ -2131,7 +2124,12 @@ build_sched_domains(const struct cpumask *cpu_map, struct sched_domain_attr *att > > sd = NULL; > for_each_sd_topology(tl) { > - > +#ifdef CONFIG_NUMA > + /* > + * Ugly hack to pass state to sd_numa_mask()... > + */ > + sched_domains_curr_level = tl->numa_level; > +#endif > if (WARN_ON(!topology_span_sane(tl, cpu_map, i))) > goto error; > > I tested with the above patch too. However it still not helping. Here is the log from my testing. At Boot. (Do remember to arrive at sched_max_numa_levels we faked the numa_distance of node 1 to be at 20 from node 0. All other offline nodes are at a distance of 10 from node 0.) numactl -H available: 2 nodes (0,5) node 0 cpus: 0 1 2 3 4 5 6 7 node 0 size: 0 MB node 0 free: 0 MB node 5 cpus: node 5 size: 32038 MB node 5 free: 29367 MB node distances: node 0 5 0: 10 40 5: 40 10 ------------------------------------------------------------------ grep -r . /sys/kernel/debug/sched/domains/cpu0/domain{0,1,2,3,4}/{name,flags} /sys/kernel/debug/sched/domains/cpu0/domain0/name:SMT /sys/kernel/debug/sched/domains/cpu0/domain0/flags:SD_BALANCE_NEWIDLE SD_BALANCE_EXEC SD_BALANCE_FORK SD_WAKE_AFFINE SD_SHARE_CPUCAPACITY SD_SHARE_PKG_RESOURCES SD_PREFER_SIBLING /sys/kernel/debug/sched/domains/cpu0/domain1/name:CACHE /sys/kernel/debug/sched/domains/cpu0/domain1/flags:SD_BALANCE_NEWIDLE SD_BALANCE_EXEC SD_BALANCE_FORK SD_WAKE_AFFINE SD_SHARE_PKG_RESOURCES SD_PREFER_SIBLING ------------------------------------------------------------------ awk '/domain/{print $1, $2}' /proc/schedstat | sort -u | sed -e 's/00000000,//g' domain0 00000055 domain0 000000aa domain1 000000ff ================================================================== (After performing smt mode switch to 1 and adding 2 additional small cores. (We always add 2 small cores at a time.)) numactl -H available: 2 nodes (0,5) node 0 cpus: 0 node 0 size: 0 MB node 0 free: 0 MB node 5 cpus: 8 9 10 11 12 13 14 15 node 5 size: 32038 MB node 5 free: 29389 MB node distances: node 0 5 0: 10 40 5: 40 10 ------------------------------------------------------------------ grep -r . /sys/kernel/debug/sched/domains/cpu0/domain{0,1,2,3,4}/{name,flags} /sys/kernel/debug/sched/domains/cpu0/domain0/name:NUMA /sys/kernel/debug/sched/domains/cpu0/domain0/flags:SD_BALANCE_NEWIDLE SD_SERIALIZE SD_OVERLAP SD_NUMA ------------------------------------------------------------------ awk '/domain/{print $1, $2}' /proc/schedstat | sort -u | sed -e 's/00000000,//g' domain0 0000ff00 domain0 0000ff01 domain1 0000ff01 ================================================================== <snipped for brevity> (Penultimate successful smt mode switch + add of a core) numactl -H available: 2 nodes (0,5) node 0 cpus: 0 1 2 3 node 0 size: 0 MB node 0 free: 0 MB node 5 cpus: 8 9 10 11 16 17 18 19 24 25 26 27 32 33 34 35 40 41 42 43 48 49 50 51 56 57 58 59 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 node 5 size: 32038 MB node 5 free: 29106 MB node distances: node 0 5 0: 10 40 5: 40 10 ------------------------------------------------------------------ grep -r . /sys/kernel/debug/sched/domains/cpu0/domain{0,1,2,3,4}/{name,flags} /sys/kernel/debug/sched/domains/cpu0/domain0/name:SMT /sys/kernel/debug/sched/domains/cpu0/domain0/flags:SD_BALANCE_NEWIDLE SD_BALANCE_EXEC SD_BALANCE_FORK SD_WAKE_AFFINE SD_SHARE_CPUCAPACITY SD_SHARE_PKG_RESOURCES SD_PREFER_SIBLING /sys/kernel/debug/sched/domains/cpu0/domain1/name:CACHE /sys/kernel/debug/sched/domains/cpu0/domain1/flags:SD_BALANCE_NEWIDLE SD_BALANCE_EXEC SD_BALANCE_FORK SD_WAKE_AFFINE SD_SHARE_PKG_RESOURCES SD_PREFER_SIBLING /sys/kernel/debug/sched/domains/cpu0/domain2/name:NUMA /sys/kernel/debug/sched/domains/cpu0/domain2/flags:SD_BALANCE_NEWIDLE SD_SERIALIZE SD_OVERLAP SD_NUMA ------------------------------------------------------------------ awk '/domain/{print $1, $2}' /proc/schedstat | sort -u | sed -e 's/00000000,//g' domain0 00000005 domain0 0000000a domain0 00000f00 domain0 000f0000 domain0 0f000000 domain0 0000000f,00000000 domain0 00000f00,00000000 domain0 000f0000,00000000 domain0 8f000000,00000000 domain0 000000ff,00000000 domain0 0000ff00,00000000 domain1 0000000f domain1 0000ffff,8f0f0f0f,0f0f0f00 domain2 0000ffff,8f0f0f0f,0f0f0f0f ================================================================== (Before Last successful smt mode switch and 2 small core additions. Till now all CPU additions have been from nodes which are online.) numactl -H available: 2 nodes (0,5) node 0 cpus: 0 1 2 3 4 5 node 0 size: 0 MB node 0 free: 0 MB node 5 cpus: 8 9 10 11 16 17 18 19 24 25 26 27 32 33 34 35 40 41 42 43 48 49 50 51 56 57 58 59 64 65 66 67 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 node 5 size: 32038 MB node 5 free: 29099 MB node distances: node 0 5 0: 10 40 5: 40 10 ------------------------------------------------------------------ grep -r . /sys/kernel/debug/sched/domains/cpu0/domain{0,1,2,3,4}/{name,flags} /sys/kernel/debug/sched/domains/cpu0/domain0/name:SMT /sys/kernel/debug/sched/domains/cpu0/domain0/flags:SD_BALANCE_NEWIDLE SD_BALANCE_EXEC SD_BALANCE_FORK SD_WAKE_AFFINE SD_SHARE_CPUCAPACITY SD_SHARE_PKG_RESOURCES SD_PREFER_SIBLING /sys/kernel/debug/sched/domains/cpu0/domain1/name:CACHE /sys/kernel/debug/sched/domains/cpu0/domain1/flags:SD_BALANCE_NEWIDLE SD_BALANCE_EXEC SD_BALANCE_FORK SD_WAKE_AFFINE SD_SHARE_PKG_RESOURCES SD_PREFER_SIBLING /sys/kernel/debug/sched/domains/cpu0/domain2/name:NUMA /sys/kernel/debug/sched/domains/cpu0/domain2/flags:SD_BALANCE_NEWIDLE SD_SERIALIZE SD_OVERLAP SD_NUMA ------------------------------------------------------------------ awk '/domain/{print $1, $2}' /proc/schedstat | sort -u | sed -e 's/00000000,//g' domain0 00000015 domain0 0000002a domain0 00000f00 domain0 000f0000 domain0 0f000000 domain0 0000000f,00000000 domain0 00000f00,00000000 domain0 000f0000,00000000 domain0 0f000000,00000000 domain0 0000000f,00000000 domain0 0000ff00,00000000 domain0 00ff0000,00000000 domain1 0000003f domain1 00ffff0f,0f0f0f0f,0f0f0f00 domain2 00ffff0f,0f0f0f0f,0f0f0f3f ================================================================== ( First addition of a CPU to a non-online node esp node whose node distance was not faked.) numactl -H available: 3 nodes (0,5,7) node 0 cpus: 0 1 2 3 4 5 6 7 node 0 size: 0 MB node 0 free: 0 MB node 5 cpus: 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 32 33 34 35 40 41 42 43 48 49 50 51 56 57 58 59 64 65 66 67 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 node 5 size: 32038 MB node 5 free: 29024 MB node 7 cpus: 88 89 90 91 92 93 94 95 node 7 size: 0 MB node 7 free: 0 MB node distances: node 0 5 7 0: 10 40 40 5: 40 10 20 7: 40 20 10 ------------------------------------------------------------------ grep -r . /sys/kernel/debug/sched/domains/cpu0/domain{0,1,2,3,4}/{name,flags} ------------------------------------------------------------------ awk '/domain/{print $1, $2}' /proc/schedstat | sort -u | sed -e 's/00000000,//g' ================================================================== I had added a debug patch to dump some variables that may help to understand the problem ------------------->8--------------------------------------------8<---------- diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c index 5e1abd9a8cc5..146f59381bcc 100644 --- a/kernel/sched/topology.c +++ b/kernel/sched/topology.c @@ -2096,7 +2096,8 @@ static bool topology_span_sane(struct sched_domain_topology_level *tl, cpumask_and(intersect, tl->mask(cpu), tl->mask(i)); if (!cpumask_equal(tl->mask(cpu), tl->mask(i)) && cpumask_intersects(intersect, cpu_map)) { - pr_err("name=%s mask(%d/%d)=%*pbl mask(%d/%d)=%*pbl", tl->name, cpu, cpu_to_node(cpu), cpumask_pr_args(tl->mask(cpu)), i, cpu_to_node(i), cpumask_pr_args(tl->mask(i))); + pr_err("name=%s mask(%d/%d)=%*pbl mask(%d/%d)=%*pbl numa-level=%d curr_level=%d", tl->name, cpu, cpu_to_node(cpu), cpumask_pr_args(tl->mask(cpu)), i, cpu_to_node(i), cpumask_pr_args(tl->mask(i)), tl->numa_level, sched_domains_curr_level); + pr_err("intersect=%*pbl cpu_map=%*pbl", cpumask_pr_args(intersect), cpumask_pr_args(cpu_map)); return false; } } ------------------->8--------------------------------------------8<---------- From dmesg: [ 99.076892] WARNING: workqueue cpumask: online intersect > possible intersect [ 167.256079] Built 2 zonelists, mobility grouping on. Total pages: 508394 [ 167.256108] Policy zone: Normal [ 167.626915] name=NODE mask(0/0)=0-7 mask(88/7)=0-7,88 numa-level=0 curr_level=0 <-- hunk above [ 167.626925] intersect=0-7 cpu_map=0-19,24-27,32-35,40-43,48-51,56-59,64-67,72-88 [ 167.626951] ------------[ cut here ]------------ [ 167.626959] WARNING: CPU: 88 PID: 6285 at kernel/sched/topology.c:2143 build_sched_domains+0xacc/0x1780 [ 167.626975] Modules linked in: rpadlpar_io rpaphp mptcp_diag xsk_diag tcp_diag udp_diag raw_diag inet_diag unix_diag af_packet_diag netlink_diag bonding tls nft_fib_inet nft_fib_ipv4 nft_fib_ipv6 nft_fib nft_reject_inet nf_reject_ipv4 nf_reject_ipv6 nft_reject nft_ct nft_chain_nat nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 ip_set rfkill nf_tables nfnetlink pseries_rng xts vmx_crypto uio_pdrv_genirq uio binfmt_misc ip_tables xfs libcrc32c dm_service_time sd_mod t10_pi sg ibmvfc scsi_transport_fc ibmveth dm_multipath dm_mirror dm_region_hash dm_log dm_mod fuse [ 167.627068] CPU: 88 PID: 6285 Comm: kworker/88:0 Tainted: G W 5.13.0-rc6+ #60 [ 167.627075] Workqueue: events cpuset_hotplug_workfn [ 167.627085] NIP: c0000000001caf3c LR: c0000000001caf38 CTR: 00000000007088ec [ 167.627091] REGS: c0000000aa253260 TRAP: 0700 Tainted: G W (5.13.0-rc6+) [ 167.627095] MSR: 8000000000029033 <SF,EE,ME,IR,DR,RI,LE> CR: 48848222 XER: 00000004 [ 167.627108] CFAR: c0000000001eac38 IRQMASK: 0 GPR00: c0000000001caf38 c0000000aa253500 c000000001c4a500 0000000000000044 GPR04: 00000000fff7ffff c0000000aa253210 0000000000000027 c0000007d9807f90 GPR08: 0000000000000023 0000000000000001 0000000000000027 c0000007d2ffffe8 GPR12: 0000000000008000 c00000001e9aa480 c000000001c93060 c00000006b834e80 GPR16: c000000001d3c6b0 0000000000000000 c000000001775860 c000000001775868 GPR20: 0000000000000000 c00000000c064900 0000000000000280 c0000000010bf838 GPR24: 0000000000000280 c000000001d3c6c0 0000000000000007 0000000000000058 GPR28: 0000000000000000 c00000000c446cc0 c000000001c978a0 c0000000b0a36f00 [ 167.627161] NIP [c0000000001caf3c] build_sched_domains+0xacc/0x1780 [ 167.627166] LR [c0000000001caf38] build_sched_domains+0xac8/0x1780 [ 167.627172] Call Trace: [ 167.627174] [c0000000aa253500] [c0000000001caf38] build_sched_domains+0xac8/0x1780 (unreliable) [ 167.627182] [c0000000aa253680] [c0000000001ccf2c] partition_sched_domains_locked+0x3ac/0x4c0 [ 167.627188] [c0000000aa253710] [c000000000280a84] rebuild_sched_domains_locked+0x404/0x9e0 [ 167.627194] [c0000000aa253810] [c000000000284400] rebuild_sched_domains+0x40/0x70 [ 167.627201] [c0000000aa253840] [c0000000002846c4] cpuset_hotplug_workfn+0x294/0xf10 [ 167.627208] [c0000000aa253c60] [c000000000175140] process_one_work+0x290/0x590 [ 167.627217] [c0000000aa253d00] [c0000000001754c8] worker_thread+0x88/0x620 [ 167.627224] [c0000000aa253da0] [c000000000181804] kthread+0x194/0x1a0 [ 167.627230] [c0000000aa253e10] [c00000000000ccec] ret_from_kernel_thread+0x5c/0x70 [ 167.627238] Instruction dump: [ 167.627242] 38635150 f9610070 4801fcdd 60000000 80de0000 3c62ff47 7f25cb78 7fe7fb78 [ 167.627252] 386351a0 7cc43378 4801fcbd 60000000 <0fe00000> 3920fff4 f92100c0 e86100e0 [ 167.627262] ---[ end trace 870f890d7c623d18 ]--- [ 168.026621] name=NODE mask(0/0)=0-7 mask(88/7)=0-7,88-89 numa-level=0 curr_level=0 [ 168.026626] intersect=0-7 cpu_map=0-19,24-27,32-35,40-43,48-51,56-59,64-67,72-89 [ 168.026637] ------------[ cut here ]------------ [ 168.026643] WARNING: CPU: 89 PID: 6298 at kernel/sched/topology.c:2143 build_sched_domains+0xacc/0x1780 [ 168.026650] Modules linked in: rpadlpar_io rpaphp mptcp_diag xsk_diag tcp_diag udp_diag raw_diag inet_diag unix_diag af_packet_diag netlink_diag bonding tls nft_fib_inet nft_fib_ipv4 nft_fib_ipv6 nft_fib nft_reject_inet nf_reject_ipv4 nf_reject_ipv6 nft_reject nft_ct nft_chain_nat nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 ip_set rfkill nf_tables nfnetlink pseries_rng xts vmx_crypto uio_pdrv_genirq uio binfmt_misc ip_tables xfs libcrc32c dm_service_time sd_mod t10_pi sg ibmvfc scsi_transport_fc ibmveth dm_multipath dm_mirror dm_region_hash dm_log dm_mod fuse [ 168.026707] CPU: 89 PID: 6298 Comm: kworker/89:0 Tainted: G W 5.13.0-rc6+ #60 [ 168.026713] Workqueue: events cpuset_hotplug_workfn [ 168.026719] NIP: c0000000001caf3c LR: c0000000001caf38 CTR: 00000000007088ec [ 168.026723] REGS: c0000000ae6d7260 TRAP: 0700 Tainted: G W (5.13.0-rc6+) [ 168.026728] MSR: 8000000000029033 <SF,EE,ME,IR,DR,RI,LE> CR: 48848222 XER: 00000007 [ 168.026738] CFAR: c0000000001eac38 IRQMASK: 0 GPR00: c0000000001caf38 c0000000ae6d7500 c000000001c4a500 0000000000000044 GPR04: 00000000fff7ffff c0000000ae6d7210 0000000000000027 c0000007d9907f90 GPR08: 0000000000000023 0000000000000001 0000000000000027 c0000007d2ffffe8 GPR12: 0000000000008000 c00000001e9a9400 c000000001c93060 c00000006b836a80 GPR16: c000000001d3c6b0 0000000000000000 c000000001775860 c000000001775868 GPR20: 0000000000000000 c00000000c064900 0000000000000280 c0000000010bf838 GPR24: 0000000000000280 c000000001d3c6c0 0000000000000007 0000000000000058 GPR28: 0000000000000000 c00000000c446cc0 c000000001c978a0 c0000000b1c13b00 [ 168.026792] NIP [c0000000001caf3c] build_sched_domains+0xacc/0x1780 [ 168.026796] LR [c0000000001caf38] build_sched_domains+0xac8/0x1780 [ 168.026801] Call Trace: [ 168.026804] [c0000000ae6d7500] [c0000000001caf38] build_sched_domains+0xac8/0x1780 (unreliable) [ 168.026811] [c0000000ae6d7680] [c0000000001ccf2c] partition_sched_domains_locked+0x3ac/0x4c0 [ 168.026817] [c0000000ae6d7710] [c000000000280a84] rebuild_sched_domains_locked+0x404/0x9e0 [ 168.026823] [c0000000ae6d7810] [c000000000284400] rebuild_sched_domains+0x40/0x70 [ 168.026829] [c0000000ae6d7840] [c0000000002846c4] cpuset_hotplug_workfn+0x294/0xf10 [ 168.026835] [c0000000ae6d7c60] [c000000000175140] process_one_work+0x290/0x590 [ 168.026841] [c0000000ae6d7d00] [c0000000001754c8] worker_thread+0x88/0x620 [ 168.026848] [c0000000ae6d7da0] [c000000000181804] kthread+0x194/0x1a0 [ 168.026853] [c0000000ae6d7e10] [c00000000000ccec] ret_from_kernel_thread+0x5c/0x70 [ 168.026859] Instruction dump: [ 168.026863] 38635150 f9610070 4801fcdd 60000000 80de0000 3c62ff47 7f25cb78 7fe7fb78 [ 168.026872] 386351a0 7cc43378 4801fcbd 60000000 <0fe00000> 3920fff4 f92100c0 e86100e0 [ 168.026883] ---[ end trace 870f890d7c623d19 ]--- Now this keeps repeating. I know I have mentioned this before. (So sorry for repeating) Generally on Power node distance is not populated for offline nodes. However to arrive at sched_max_numa_levels, we thought of faking few node distances. In the above case, we faked distance of node 1 as 20 (from node 0) node 5 was already at distance of 40 from node 0. So when sched_domains_numa_masks_set is called to update sd_numa_mask or sched_domains_numa_masks, all CPUs under node 0 get updated for node 2 too. (since node 2 is shown as at a local distance from node 0). Do look at the node mask of CPU 88 in the dmesg. It should have been 88, however its 0-7,88 where 0-7 are coming from node 0. Even if we skip updation of sched_domains_numa_masks for offline nodes, on online of a node (i.e when we get the correct node distance), we have to update the sched_domains_numa_masks to ensure CPUs that were already present within a certain distance and skipped are added back. And this was what I tried to do in my patch.
* Srikar Dronamraju <srikar@linux.vnet.ibm.com> [2021-07-23 20:09:14]: > * Valentin Schneider <valentin.schneider@arm.com> [2021-07-13 17:32:14]: > > > On 12/07/21 18:18, Srikar Dronamraju wrote: > > > Hi Valentin, > > > > > >> On 01/07/21 09:45, Srikar Dronamraju wrote: > > >> > @@ -1891,12 +1894,30 @@ void sched_init_numa(void) > > >> > void sched_domains_numa_masks_set(unsigned int cpu) > > >> > { > > > Hey Valentin / Peter Did you get a chance to look at this?
On 04/08/21 15:31, Srikar Dronamraju wrote: > * Srikar Dronamraju <srikar@linux.vnet.ibm.com> [2021-07-23 20:09:14]: > >> * Valentin Schneider <valentin.schneider@arm.com> [2021-07-13 17:32:14]: >> >> > On 12/07/21 18:18, Srikar Dronamraju wrote: >> > > Hi Valentin, >> > > >> > >> On 01/07/21 09:45, Srikar Dronamraju wrote: >> > >> > @@ -1891,12 +1894,30 @@ void sched_init_numa(void) >> > >> > void sched_domains_numa_masks_set(unsigned int cpu) >> > >> > { >> > > > > Hey Valentin / Peter > > Did you get a chance to look at this? > Barely, I wanted to set some time aside to stare at this and have been failing miserably. Let me bump it up my todolist, I'll get to it before the end of the week. > -- > Thanks and Regards > Srikar Dronamraju
A bit late, but technically the week isn't over yet! :D On 23/07/21 20:09, Srikar Dronamraju wrote: > * Valentin Schneider <valentin.schneider@arm.com> [2021-07-13 17:32:14]: >> Now, let's take examples from your cover letter: >> >> node distances: >> node 0 1 2 3 4 5 6 7 >> 0: 10 20 40 40 40 40 40 40 >> 1: 20 10 40 40 40 40 40 40 >> 2: 40 40 10 20 40 40 40 40 >> 3: 40 40 20 10 40 40 40 40 >> 4: 40 40 40 40 10 20 40 40 >> 5: 40 40 40 40 20 10 40 40 >> 6: 40 40 40 40 40 40 10 20 >> 7: 40 40 40 40 40 40 20 10 >> >> But the system boots with just nodes 0 and 1, thus only this distance >> matrix is valid: >> >> node 0 1 >> 0: 10 20 >> 1: 20 10 >> >> topology_span_sane() is going to use tl->mask(cpu), and as you reported the >> NODE topology level should cause issues. Let's assume all offline nodes say >> they're 10 distance away from everyone else, and that we have one CPU per >> node. This would give us: >> > > No, > All offline nodes would be at a distance of 10 from node 0 only. > So here node distance of all offline nodes from node 1 would be 20. > >> NODE->mask(0) == 0,2-7 >> NODE->mask(1) == 1-7 > > so > > NODE->mask(0) == 0,2-7 > NODE->mask(1) should be 1 > and NODE->mask(2-7) == 0,2-7 > Ok, so that shouldn't trigger the warning. >> >> The intersection is 2-7, we'll trigger the WARN_ON(). >> Now, with the above snippet, we'll check if that intersection covers any >> online CPU. For sched_init_domains(), cpu_map is cpu_active_mask, so we'd >> end up with an empty intersection and we shouldn't warn - that's the theory >> at least. > > Now lets say we onlined CPU 3 and node 3 which was at a actual distance > of 20 from node 0. > > (If we only consider online CPUs, and since scheduler masks like > sched_domains_numa_masks arent updated with offline CPUs,) > then > > NODE->mask(0) == 0 > NODE->mask(1) == 1 > NODE->mask(3) == 0,3 > Wait, doesn't the distance matrix (without any offline node) say distance(0, 3) == 40 ? We should have at the very least: node 0 1 2 3 0: 10 20 ?? 40 1: 20 20 ?? 40 2: ?? ?? ?? ?? 3: 40 40 ?? 10 Regardless, NODE->mask(x) is sched_domains_numa_masks[0][x], if distance(0,3) > LOCAL_DISTANCE then node0 ∉ NODE->mask(3) > cpumask_and(intersect, tl->mask(cpu), tl->mask(i)); > if (!cpumask_equal(tl->mask(cpu), tl->mask(i)) && cpumask_intersects(intersect, cpu_map)) > > cpu_map is 0,1,3 > intersect is 0 > > From above NODE->mask(0) is !equal to NODE->mask(1) and > cpumask_intersects(intersect, cpu_map) is also true. > > I picked Node 3 since if Node 1 is online, we would have faked distance > for Node 2 to be at distance of 40. > > Any node from 3 to 7, we would have faced the same problem. > >> >> Looking at sd_numa_mask(), I think there's a bug with topology_span_sane(): >> it doesn't run in the right place wrt where sched_domains_curr_level is >> updated. Could you try the below on top of the previous snippet? >> >> If that doesn't help, could you share the node distances / topology masks >> that lead to the WARN_ON()? Thanks. >> >> --- >> diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c >> index b77ad49dc14f..cda69dfa4065 100644 >> --- a/kernel/sched/topology.c >> +++ b/kernel/sched/topology.c >> @@ -1516,13 +1516,6 @@ sd_init(struct sched_domain_topology_level *tl, >> int sd_id, sd_weight, sd_flags = 0; >> struct cpumask *sd_span; >> >> -#ifdef CONFIG_NUMA >> - /* >> - * Ugly hack to pass state to sd_numa_mask()... >> - */ >> - sched_domains_curr_level = tl->numa_level; >> -#endif >> - >> sd_weight = cpumask_weight(tl->mask(cpu)); >> >> if (tl->sd_flags) >> @@ -2131,7 +2124,12 @@ build_sched_domains(const struct cpumask *cpu_map, struct sched_domain_attr *att >> >> sd = NULL; >> for_each_sd_topology(tl) { >> - >> +#ifdef CONFIG_NUMA >> + /* >> + * Ugly hack to pass state to sd_numa_mask()... >> + */ >> + sched_domains_curr_level = tl->numa_level; >> +#endif >> if (WARN_ON(!topology_span_sane(tl, cpu_map, i))) >> goto error; >> >> > > I tested with the above patch too. However it still not helping. > > Here is the log from my testing. > > At Boot. > > (Do remember to arrive at sched_max_numa_levels we faked the > numa_distance of node 1 to be at 20 from node 0. All other offline > nodes are at a distance of 10 from node 0.) > [...] > ( First addition of a CPU to a non-online node esp node whose node > distance was not faked.) > > numactl -H > available: 3 nodes (0,5,7) > node 0 cpus: 0 1 2 3 4 5 6 7 > node 0 size: 0 MB > node 0 free: 0 MB > node 5 cpus: 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 32 33 34 35 40 41 42 43 48 49 50 51 56 57 58 59 64 65 66 67 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 > node 5 size: 32038 MB > node 5 free: 29024 MB > node 7 cpus: 88 89 90 91 92 93 94 95 > node 7 size: 0 MB > node 7 free: 0 MB > node distances: > node 0 5 7 > 0: 10 40 40 > 5: 40 10 20 > 7: 40 20 10 > ------------------------------------------------------------------ > grep -r . /sys/kernel/debug/sched/domains/cpu0/domain{0,1,2,3,4}/{name,flags} > ------------------------------------------------------------------ > awk '/domain/{print $1, $2}' /proc/schedstat | sort -u | sed -e 's/00000000,//g' > ================================================================== > > I had added a debug patch to dump some variables that may help to > understand the problem > ------------------->8--------------------------------------------8<---------- > diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c > index 5e1abd9a8cc5..146f59381bcc 100644 > --- a/kernel/sched/topology.c > +++ b/kernel/sched/topology.c > @@ -2096,7 +2096,8 @@ static bool topology_span_sane(struct sched_domain_topology_level *tl, > cpumask_and(intersect, tl->mask(cpu), tl->mask(i)); > if (!cpumask_equal(tl->mask(cpu), tl->mask(i)) && > cpumask_intersects(intersect, cpu_map)) { > - pr_err("name=%s mask(%d/%d)=%*pbl mask(%d/%d)=%*pbl", tl->name, cpu, cpu_to_node(cpu), cpumask_pr_args(tl->mask(cpu)), i, cpu_to_node(i), cpumask_pr_args(tl->mask(i))); > + pr_err("name=%s mask(%d/%d)=%*pbl mask(%d/%d)=%*pbl numa-level=%d curr_level=%d", tl->name, cpu, cpu_to_node(cpu), cpumask_pr_args(tl->mask(cpu)), i, cpu_to_node(i), cpumask_pr_args(tl->mask(i)), tl->numa_level, sched_domains_curr_level); > + pr_err("intersect=%*pbl cpu_map=%*pbl", cpumask_pr_args(intersect), cpumask_pr_args(cpu_map)); > return false; > } > } > ------------------->8--------------------------------------------8<---------- > > From dmesg: > > [ 167.626915] name=NODE mask(0/0)=0-7 mask(88/7)=0-7,88 numa-level=0 curr_level=0 <-- hunk above > [ 167.626925] intersect=0-7 cpu_map=0-19,24-27,32-35,40-43,48-51,56-59,64-67,72-88 > [ 168.026621] name=NODE mask(0/0)=0-7 mask(88/7)=0-7,88-89 numa-level=0 curr_level=0 > [ 168.026626] intersect=0-7 cpu_map=0-19,24-27,32-35,40-43,48-51,56-59,64-67,72-89 > Ok so to condense the info, we have: node 0 5 7 0: 10 40 40 5: 40 10 20 7: 40 20 10 node0: 0-7 node5: 8-29, 32-35, 40-43, 48-51, 56-59, 64-67, 72-87 node7: 88-95 With the above distance map, we should have NODE->mask(CPU0) == 0-7 NODE->mask(CPU8) == 8-29, 32-35, 40-43, 48-51, 56-59, 64-67, 72-87 NODE->mask(CPU88) == 88-95 (this is sched_domains_numa_masks[0][CPUx], and sched_domains_numa_distance[0] == LOCAL_DISTANCE, thus the mask of CPUs LOCAL_DISTANCE away from CPUx). For some reason you end up with node0 being part of node7's NODE mask. Neither nodes are offline, and per the above distance table that shouldn't happen. > Now this keeps repeating. > > I know I have mentioned this before. (So sorry for repeating) It can't hurt to reformulate ;) > Generally on Power node distance is not populated for offline nodes. > However to arrive at sched_max_numa_levels, we thought of faking few > node distances. In the above case, we faked distance of node 1 as 20 > (from node 0) node 5 was already at distance of 40 from node 0. > Right, again that gives us the right set of unique distances (10, 20, 40). > So when sched_domains_numa_masks_set is called to update sd_numa_mask or > sched_domains_numa_masks, all CPUs under node 0 get updated for node 2 > too. (since node 2 is shown as at a local distance from node 0). Do > look at the node mask of CPU 88 in the dmesg. It should have been 88, > however its 0-7,88 where 0-7 are coming from node 0. > > Even if we skip updation of sched_domains_numa_masks for offline nodes, > on online of a node (i.e when we get the correct node distance), we have > to update the sched_domains_numa_masks to ensure CPUs that were already > present within a certain distance and skipped are added back. And this > was what I tried to do in my patch. > Ok, so it looks like we really can't do without that part - even if we get "sensible" distance values for the online nodes, we can't divine values for the offline ones. > -- > Thanks and Regards > Srikar Dronamraju
* Valentin Schneider <valentin.schneider@arm.com> [2021-08-08 16:56:47]: > > A bit late, but technically the week isn't over yet! :D > > On 23/07/21 20:09, Srikar Dronamraju wrote: > > * Valentin Schneider <valentin.schneider@arm.com> [2021-07-13 17:32:14]: > >> Now, let's take examples from your cover letter: > >> > >> node distances: > >> node 0 1 2 3 4 5 6 7 > >> 0: 10 20 40 40 40 40 40 40 > >> 1: 20 10 40 40 40 40 40 40 > >> 2: 40 40 10 20 40 40 40 40 > >> 3: 40 40 20 10 40 40 40 40 > >> 4: 40 40 40 40 10 20 40 40 > >> 5: 40 40 40 40 20 10 40 40 > >> 6: 40 40 40 40 40 40 10 20 > >> 7: 40 40 40 40 40 40 20 10 > >> > >> But the system boots with just nodes 0 and 1, thus only this distance > >> matrix is valid: > >> > >> node 0 1 > >> 0: 10 20 > >> 1: 20 10 > >> > >> topology_span_sane() is going to use tl->mask(cpu), and as you reported the > >> NODE topology level should cause issues. Let's assume all offline nodes say > >> they're 10 distance away from everyone else, and that we have one CPU per > >> node. This would give us: > >> > > > > No, > > All offline nodes would be at a distance of 10 from node 0 only. > > So here node distance of all offline nodes from node 1 would be 20. > > > >> NODE->mask(0) == 0,2-7 > >> NODE->mask(1) == 1-7 > > > > so > > > > NODE->mask(0) == 0,2-7 > > NODE->mask(1) should be 1 > > and NODE->mask(2-7) == 0,2-7 > > > > Ok, so that shouldn't trigger the warning. Yes not at this point, but later on when we online a node. > > >> > >> The intersection is 2-7, we'll trigger the WARN_ON(). > >> Now, with the above snippet, we'll check if that intersection covers any > >> online CPU. For sched_init_domains(), cpu_map is cpu_active_mask, so we'd > >> end up with an empty intersection and we shouldn't warn - that's the theory > >> at least. > > > > Now lets say we onlined CPU 3 and node 3 which was at a actual distance > > of 20 from node 0. > > > > (If we only consider online CPUs, and since scheduler masks like > > sched_domains_numa_masks arent updated with offline CPUs,) > > then > > > > NODE->mask(0) == 0 > > NODE->mask(1) == 1 > > NODE->mask(3) == 0,3 > > > > Wait, doesn't the distance matrix (without any offline node) say > > distance(0, 3) == 40 > > ? We should have at the very least: > > node 0 1 2 3 > 0: 10 20 ?? 40 > 1: 20 20 ?? 40 > 2: ?? ?? ?? ?? > 3: 40 40 ?? 10 > Before onlining node 3 and CPU 3 (node/CPU 0 and 1 are already online) Note: Node 2-7 and CPU 2-7 are still offline. node 0 1 2 3 0: 10 20 40 10 1: 20 20 40 10 2: 40 40 10 10 3: 10 10 10 10 NODE->mask(0) == 0 NODE->mask(1) == 1 NODE->mask(2) == 0 NODE->mask(3) == 0 Note: This is with updating Node 2's distance as 40 for figuring out the number of numa levels. Since we have all possible distances, we dont update Node 3 distance, so it will be as if its local to node 0. Now when Node 3 and CPU 3 are onlined Note: Node 2, 3-7 and CPU 2, 3-7 are still offline. node 0 1 2 3 0: 10 20 40 40 1: 20 20 40 40 2: 40 40 10 40 3: 40 40 40 10 NODE->mask(0) == 0 NODE->mask(1) == 1 NODE->mask(2) == 0 NODE->mask(3) == 0,3 CPU 0 continues to be part of Node->mask(3) because when we online and we find the right distance, there is no API to reset the numa mask of 3 to remove CPU 0 from the numa masks. If we had an API to clear/set sched_domains_numa_masks[node][] when the node state changes, we could probably plug-in to clear/set the node masks whenever node state changes. > Regardless, NODE->mask(x) is sched_domains_numa_masks[0][x], if > > distance(0,3) > LOCAL_DISTANCE > > then > > node0 ??? NODE->mask(3) > > > cpumask_and(intersect, tl->mask(cpu), tl->mask(i)); > > if (!cpumask_equal(tl->mask(cpu), tl->mask(i)) && cpumask_intersects(intersect, cpu_map)) > > > > cpu_map is 0,1,3 > > intersect is 0 > > > > From above NODE->mask(0) is !equal to NODE->mask(1) and > > cpumask_intersects(intersect, cpu_map) is also true. > > > > I picked Node 3 since if Node 1 is online, we would have faked distance > > for Node 2 to be at distance of 40. > > > > Any node from 3 to 7, we would have faced the same problem. > > > >> > >> Looking at sd_numa_mask(), I think there's a bug with topology_span_sane(): > >> it doesn't run in the right place wrt where sched_domains_curr_level is > >> updated. Could you try the below on top of the previous snippet? > >> > >> If that doesn't help, could you share the node distances / topology masks > >> that lead to the WARN_ON()? Thanks. > >> > >> --- > >> diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c > >> index b77ad49dc14f..cda69dfa4065 100644 > >> --- a/kernel/sched/topology.c > >> +++ b/kernel/sched/topology.c > >> @@ -1516,13 +1516,6 @@ sd_init(struct sched_domain_topology_level *tl, > >> int sd_id, sd_weight, sd_flags = 0; > >> struct cpumask *sd_span; > >> > >> -#ifdef CONFIG_NUMA > >> - /* > >> - * Ugly hack to pass state to sd_numa_mask()... > >> - */ > >> - sched_domains_curr_level = tl->numa_level; > >> -#endif > >> - > >> sd_weight = cpumask_weight(tl->mask(cpu)); > >> > >> if (tl->sd_flags) > >> @@ -2131,7 +2124,12 @@ build_sched_domains(const struct cpumask *cpu_map, struct sched_domain_attr *att > >> > >> sd = NULL; > >> for_each_sd_topology(tl) { > >> - > >> +#ifdef CONFIG_NUMA > >> + /* > >> + * Ugly hack to pass state to sd_numa_mask()... > >> + */ > >> + sched_domains_curr_level = tl->numa_level; > >> +#endif > >> if (WARN_ON(!topology_span_sane(tl, cpu_map, i))) > >> goto error; > >> > >> > > > > I tested with the above patch too. However it still not helping. > > > > Here is the log from my testing. > > > > At Boot. > > > > (Do remember to arrive at sched_max_numa_levels we faked the > > numa_distance of node 1 to be at 20 from node 0. All other offline > > nodes are at a distance of 10 from node 0.) > > > > [...] > > > ( First addition of a CPU to a non-online node esp node whose node > > distance was not faked.) > > > > numactl -H > > available: 3 nodes (0,5,7) > > node 0 cpus: 0 1 2 3 4 5 6 7 > > node 0 size: 0 MB > > node 0 free: 0 MB > > node 5 cpus: 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 32 33 34 35 40 41 42 43 48 49 50 51 56 57 58 59 64 65 66 67 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 > > node 5 size: 32038 MB > > node 5 free: 29024 MB > > node 7 cpus: 88 89 90 91 92 93 94 95 > > node 7 size: 0 MB > > node 7 free: 0 MB > > node distances: > > node 0 5 7 > > 0: 10 40 40 > > 5: 40 10 20 > > 7: 40 20 10 > > ------------------------------------------------------------------ > > grep -r . /sys/kernel/debug/sched/domains/cpu0/domain{0,1,2,3,4}/{name,flags} > > ------------------------------------------------------------------ > > awk '/domain/{print $1, $2}' /proc/schedstat | sort -u | sed -e 's/00000000,//g' > > ================================================================== > > > > I had added a debug patch to dump some variables that may help to > > understand the problem > > ------------------->8--------------------------------------------8<---------- > > diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c > > index 5e1abd9a8cc5..146f59381bcc 100644 > > --- a/kernel/sched/topology.c > > +++ b/kernel/sched/topology.c > > @@ -2096,7 +2096,8 @@ static bool topology_span_sane(struct sched_domain_topology_level *tl, > > cpumask_and(intersect, tl->mask(cpu), tl->mask(i)); > > if (!cpumask_equal(tl->mask(cpu), tl->mask(i)) && > > cpumask_intersects(intersect, cpu_map)) { > > - pr_err("name=%s mask(%d/%d)=%*pbl mask(%d/%d)=%*pbl", tl->name, cpu, cpu_to_node(cpu), cpumask_pr_args(tl->mask(cpu)), i, cpu_to_node(i), cpumask_pr_args(tl->mask(i))); > > + pr_err("name=%s mask(%d/%d)=%*pbl mask(%d/%d)=%*pbl numa-level=%d curr_level=%d", tl->name, cpu, cpu_to_node(cpu), cpumask_pr_args(tl->mask(cpu)), i, cpu_to_node(i), cpumask_pr_args(tl->mask(i)), tl->numa_level, sched_domains_curr_level); > > + pr_err("intersect=%*pbl cpu_map=%*pbl", cpumask_pr_args(intersect), cpumask_pr_args(cpu_map)); > > return false; > > } > > } > > ------------------->8--------------------------------------------8<---------- > > > > From dmesg: > > > > [ 167.626915] name=NODE mask(0/0)=0-7 mask(88/7)=0-7,88 numa-level=0 curr_level=0 <-- hunk above > > [ 167.626925] intersect=0-7 cpu_map=0-19,24-27,32-35,40-43,48-51,56-59,64-67,72-88 > > > [ 168.026621] name=NODE mask(0/0)=0-7 mask(88/7)=0-7,88-89 numa-level=0 curr_level=0 > > [ 168.026626] intersect=0-7 cpu_map=0-19,24-27,32-35,40-43,48-51,56-59,64-67,72-89 > > > > Ok so to condense the info, we have: > > node 0 5 7 > 0: 10 40 40 > 5: 40 10 20 > 7: 40 20 10 > > node0: 0-7 > node5: 8-29, 32-35, 40-43, 48-51, 56-59, 64-67, 72-87 > node7: 88-95 > > With the above distance map, we should have > > node->mask(cpu0) == 0-7 > node->mask(cpu8) == 8-29, 32-35, 40-43, 48-51, 56-59, 64-67, 72-87 > node->mask(cpu88) == 88-95 > Yes. this is what we should have and node->mask(cpu0) == 0-7 node->mask(cpu8) == 8-29, 32-35, 40-43, 48-51, 56-59, 64-67, 72-87 node->mask(cpu88) == 0-7, 88-95 this is what we get. > (this is sched_domains_numa_masks[0][CPUx], and > sched_domains_numa_distance[0] == LOCAL_DISTANCE, thus the mask of CPUs > LOCAL_DISTANCE away from CPUx). > > For some reason you end up with node0 being part of node7's NODE > mask. Neither nodes are offline, and per the above distance table that > shouldn't happen. > > > Now this keeps repeating. > > > > I know I have mentioned this before. (So sorry for repeating) > > It can't hurt to reformulate ;) > > > Generally on Power node distance is not populated for offline nodes. > > However to arrive at sched_max_numa_levels, we thought of faking few > > node distances. In the above case, we faked distance of node 1 as 20 > > (from node 0) node 5 was already at distance of 40 from node 0. > > > > Right, again that gives us the right set of unique distances (10, 20, 40). > > > So when sched_domains_numa_masks_set is called to update sd_numa_mask or > > sched_domains_numa_masks, all CPUs under node 0 get updated for node 2 > > too. (since node 2 is shown as at a local distance from node 0). Do > > look at the node mask of CPU 88 in the dmesg. It should have been 88, > > however its 0-7,88 where 0-7 are coming from node 0. > > > > Even if we skip updation of sched_domains_numa_masks for offline nodes, > > on online of a node (i.e when we get the correct node distance), we have > > to update the sched_domains_numa_masks to ensure CPUs that were already > > present within a certain distance and skipped are added back. And this > > was what I tried to do in my patch. > > > > Ok, so it looks like we really can't do without that part - even if we get > "sensible" distance values for the online nodes, we can't divine values for > the offline ones. > Yes -- Thanks and Regards Srikar Dronamraju
On 09/08/21 12:22, Srikar Dronamraju wrote: > * Valentin Schneider <valentin.schneider@arm.com> [2021-08-08 16:56:47]: >> Wait, doesn't the distance matrix (without any offline node) say >> >> distance(0, 3) == 40 >> >> ? We should have at the very least: >> >> node 0 1 2 3 >> 0: 10 20 ?? 40 >> 1: 20 20 ?? 40 >> 2: ?? ?? ?? ?? >> 3: 40 40 ?? 10 >> > > Before onlining node 3 and CPU 3 (node/CPU 0 and 1 are already online) > Note: Node 2-7 and CPU 2-7 are still offline. > > node 0 1 2 3 > 0: 10 20 40 10 > 1: 20 20 40 10 > 2: 40 40 10 10 > 3: 10 10 10 10 > > NODE->mask(0) == 0 > NODE->mask(1) == 1 > NODE->mask(2) == 0 > NODE->mask(3) == 0 > > Note: This is with updating Node 2's distance as 40 for figuring out > the number of numa levels. Since we have all possible distances, we > dont update Node 3 distance, so it will be as if its local to node 0. > > Now when Node 3 and CPU 3 are onlined > Note: Node 2, 3-7 and CPU 2, 3-7 are still offline. > > node 0 1 2 3 > 0: 10 20 40 40 > 1: 20 20 40 40 > 2: 40 40 10 40 > 3: 40 40 40 10 > > NODE->mask(0) == 0 > NODE->mask(1) == 1 > NODE->mask(2) == 0 > NODE->mask(3) == 0,3 > > CPU 0 continues to be part of Node->mask(3) because when we online and > we find the right distance, there is no API to reset the numa mask of > 3 to remove CPU 0 from the numa masks. > > If we had an API to clear/set sched_domains_numa_masks[node][] when > the node state changes, we could probably plug-in to clear/set the > node masks whenever node state changes. > Gotcha, this is now coming back to me... [...] >> Ok, so it looks like we really can't do without that part - even if we get >> "sensible" distance values for the online nodes, we can't divine values for >> the offline ones. >> > > Yes > Argh, while your approach does take care of the masks, it leaves sched_numa_topology_type unchanged. You *can* force an update of it, but yuck :( I got to the below... --- From: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Date: Thu, 1 Jul 2021 09:45:51 +0530 Subject: [PATCH 1/1] sched/topology: Skip updating masks for non-online nodes The scheduler currently expects NUMA node distances to be stable from init onwards, and as a consequence builds the related data structures once-and-for-all at init (see sched_init_numa()). Unfortunately, on some architectures node distance is unreliable for offline nodes and may very well change upon onlining. Skip over offline nodes during sched_init_numa(). Track nodes that have been onlined at least once, and trigger a build of a node's NUMA masks when it is first onlined post-init. Reported-by: Geetika Moolchandani <Geetika.Moolchandani1@ibm.com> Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Signed-off-by: Valentin Schneider <valentin.schneider@arm.com> --- kernel/sched/topology.c | 65 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 65 insertions(+) diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c index b77ad49dc14f..cba95793a9b7 100644 --- a/kernel/sched/topology.c +++ b/kernel/sched/topology.c @@ -1482,6 +1482,8 @@ int sched_max_numa_distance; static int *sched_domains_numa_distance; static struct cpumask ***sched_domains_numa_masks; int __read_mostly node_reclaim_distance = RECLAIM_DISTANCE; + +static unsigned long __read_mostly *sched_numa_onlined_nodes; #endif /* @@ -1833,6 +1835,16 @@ void sched_init_numa(void) sched_domains_numa_masks[i][j] = mask; for_each_node(k) { + /* + * Distance information can be unreliable for + * offline nodes, defer building the node + * masks to its bringup. + * This relies on all unique distance values + * still being visible at init time. + */ + if (!node_online(j)) + continue; + if (sched_debug() && (node_distance(j, k) != node_distance(k, j))) sched_numa_warn("Node-distance not symmetric"); @@ -1886,6 +1898,53 @@ void sched_init_numa(void) sched_max_numa_distance = sched_domains_numa_distance[nr_levels - 1]; init_numa_topology_type(); + + sched_numa_onlined_nodes = bitmap_alloc(nr_node_ids, GFP_KERNEL); + if (!sched_numa_onlined_nodes) + return; + + bitmap_zero(sched_numa_onlined_nodes, nr_node_ids); + for_each_online_node(i) + bitmap_set(sched_numa_onlined_nodes, i, 1); +} + +void __sched_domains_numa_masks_set(unsigned int node) +{ + int i, j; + + /* + * NUMA masks are not built for offline nodes in sched_init_numa(). + * Thus, when a CPU of a never-onlined-before node gets plugged in, + * adding that new CPU to the right NUMA masks is not sufficient: the + * masks of that CPU's node must also be updated. + */ + if (test_bit(node, sched_numa_onlined_nodes)) + return; + + bitmap_set(sched_numa_onlined_nodes, node, 1); + + for (i = 0; i < sched_domains_numa_levels; i++) { + for (j = 0; j < nr_node_ids; j++) { + if (!node_online(j) || node == j) + continue; + + if (node_distance(j, node) > sched_domains_numa_distance[i]) + continue; + + /* Add remote nodes in our masks */ + cpumask_or(sched_domains_numa_masks[i][node], + sched_domains_numa_masks[i][node], + sched_domains_numa_masks[0][j]); + } + } + + /* + * A new node has been brought up, potentially changing the topology + * classification. + * + * Note that this is racy vs any use of sched_numa_topology_type :/ + */ + init_numa_topology_type(); } void sched_domains_numa_masks_set(unsigned int cpu) @@ -1893,8 +1952,14 @@ void sched_domains_numa_masks_set(unsigned int cpu) int node = cpu_to_node(cpu); int i, j; + __sched_domains_numa_masks_set(node); + for (i = 0; i < sched_domains_numa_levels; i++) { for (j = 0; j < nr_node_ids; j++) { + if (!node_online(j)) + continue; + + /* Set ourselves in the remote node's masks */ if (node_distance(j, node) <= sched_domains_numa_distance[i]) cpumask_set_cpu(cpu, sched_domains_numa_masks[i][j]); }
* Valentin Schneider <valentin.schneider@arm.com> [2021-08-09 13:52:38]: > On 09/08/21 12:22, Srikar Dronamraju wrote: > > * Valentin Schneider <valentin.schneider@arm.com> [2021-08-08 16:56:47]: > >> Wait, doesn't the distance matrix (without any offline node) say > >> > >> distance(0, 3) == 40 > >> > >> ? We should have at the very least: > >> > >> node 0 1 2 3 > >> 0: 10 20 ?? 40 > >> 1: 20 20 ?? 40 > >> 2: ?? ?? ?? ?? > >> 3: 40 40 ?? 10 > >> > > > > Before onlining node 3 and CPU 3 (node/CPU 0 and 1 are already online) > > Note: Node 2-7 and CPU 2-7 are still offline. > > > > node 0 1 2 3 > > 0: 10 20 40 10 > > 1: 20 20 40 10 > > 2: 40 40 10 10 > > 3: 10 10 10 10 > > > > NODE->mask(0) == 0 > > NODE->mask(1) == 1 > > NODE->mask(2) == 0 > > NODE->mask(3) == 0 > > > > Note: This is with updating Node 2's distance as 40 for figuring out > > the number of numa levels. Since we have all possible distances, we > > dont update Node 3 distance, so it will be as if its local to node 0. > > > > Now when Node 3 and CPU 3 are onlined > > Note: Node 2, 3-7 and CPU 2, 3-7 are still offline. > > > > node 0 1 2 3 > > 0: 10 20 40 40 > > 1: 20 20 40 40 > > 2: 40 40 10 40 > > 3: 40 40 40 10 > > > > NODE->mask(0) == 0 > > NODE->mask(1) == 1 > > NODE->mask(2) == 0 > > NODE->mask(3) == 0,3 > > > > CPU 0 continues to be part of Node->mask(3) because when we online and > > we find the right distance, there is no API to reset the numa mask of > > 3 to remove CPU 0 from the numa masks. > > > > If we had an API to clear/set sched_domains_numa_masks[node][] when > > the node state changes, we could probably plug-in to clear/set the > > node masks whenever node state changes. > > > > Gotcha, this is now coming back to me... > > [...] > > >> Ok, so it looks like we really can't do without that part - even if we get > >> "sensible" distance values for the online nodes, we can't divine values for > >> the offline ones. > >> > > > > Yes > > > > Argh, while your approach does take care of the masks, it leaves > sched_numa_topology_type unchanged. You *can* force an update of it, but > yuck :( > > I got to the below... > Yes, I completely missed that we should update sched_numa_topology_type. > --- > From: Srikar Dronamraju <srikar@linux.vnet.ibm.com> > Date: Thu, 1 Jul 2021 09:45:51 +0530 > Subject: [PATCH 1/1] sched/topology: Skip updating masks for non-online nodes > > The scheduler currently expects NUMA node distances to be stable from init > onwards, and as a consequence builds the related data structures > once-and-for-all at init (see sched_init_numa()). > > Unfortunately, on some architectures node distance is unreliable for > offline nodes and may very well change upon onlining. > > Skip over offline nodes during sched_init_numa(). Track nodes that have > been onlined at least once, and trigger a build of a node's NUMA masks when > it is first onlined post-init. > Your version is much much better than mine. And I have verified that it works as expected. > Reported-by: Geetika Moolchandani <Geetika.Moolchandani1@ibm.com> > Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> > Signed-off-by: Valentin Schneider <valentin.schneider@arm.com> > --- > kernel/sched/topology.c | 65 +++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 65 insertions(+) > > diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c > index b77ad49dc14f..cba95793a9b7 100644 > --- a/kernel/sched/topology.c > +++ b/kernel/sched/topology.c > @@ -1482,6 +1482,8 @@ int sched_max_numa_distance; > static int *sched_domains_numa_distance; > static struct cpumask ***sched_domains_numa_masks; > int __read_mostly node_reclaim_distance = RECLAIM_DISTANCE; > + > +static unsigned long __read_mostly *sched_numa_onlined_nodes; > #endif > > /* > @@ -1833,6 +1835,16 @@ void sched_init_numa(void) > sched_domains_numa_masks[i][j] = mask; > > for_each_node(k) { > + /* > + * Distance information can be unreliable for > + * offline nodes, defer building the node > + * masks to its bringup. > + * This relies on all unique distance values > + * still being visible at init time. > + */ > + if (!node_online(j)) > + continue; > + > if (sched_debug() && (node_distance(j, k) != node_distance(k, j))) > sched_numa_warn("Node-distance not symmetric"); > > @@ -1886,6 +1898,53 @@ void sched_init_numa(void) > sched_max_numa_distance = sched_domains_numa_distance[nr_levels - 1]; > > init_numa_topology_type(); > + > + sched_numa_onlined_nodes = bitmap_alloc(nr_node_ids, GFP_KERNEL); > + if (!sched_numa_onlined_nodes) > + return; > + > + bitmap_zero(sched_numa_onlined_nodes, nr_node_ids); > + for_each_online_node(i) > + bitmap_set(sched_numa_onlined_nodes, i, 1); > +} > + > +void __sched_domains_numa_masks_set(unsigned int node) > +{ > + int i, j; > + > + /* > + * NUMA masks are not built for offline nodes in sched_init_numa(). > + * Thus, when a CPU of a never-onlined-before node gets plugged in, > + * adding that new CPU to the right NUMA masks is not sufficient: the > + * masks of that CPU's node must also be updated. > + */ > + if (test_bit(node, sched_numa_onlined_nodes)) > + return; > + > + bitmap_set(sched_numa_onlined_nodes, node, 1); > + > + for (i = 0; i < sched_domains_numa_levels; i++) { > + for (j = 0; j < nr_node_ids; j++) { > + if (!node_online(j) || node == j) > + continue; > + > + if (node_distance(j, node) > sched_domains_numa_distance[i]) > + continue; > + > + /* Add remote nodes in our masks */ > + cpumask_or(sched_domains_numa_masks[i][node], > + sched_domains_numa_masks[i][node], > + sched_domains_numa_masks[0][j]); > + } > + } > + > + /* > + * A new node has been brought up, potentially changing the topology > + * classification. > + * > + * Note that this is racy vs any use of sched_numa_topology_type :/ > + */ > + init_numa_topology_type(); > } > > void sched_domains_numa_masks_set(unsigned int cpu) > @@ -1893,8 +1952,14 @@ void sched_domains_numa_masks_set(unsigned int cpu) > int node = cpu_to_node(cpu); > int i, j; > > + __sched_domains_numa_masks_set(node); > + > for (i = 0; i < sched_domains_numa_levels; i++) { > for (j = 0; j < nr_node_ids; j++) { > + if (!node_online(j)) > + continue; > + > + /* Set ourselves in the remote node's masks */ > if (node_distance(j, node) <= sched_domains_numa_distance[i]) > cpumask_set_cpu(cpu, sched_domains_numa_masks[i][j]); > } > -- > 2.25.1 >
> > Your version is much much better than mine. > And I have verified that it works as expected. > > Hey Peter/Valentin Are we waiting for any more feedback/testing for this?
On 16/08/21 16:03, Srikar Dronamraju wrote: >> >> Your version is much much better than mine. >> And I have verified that it works as expected. >> >> > > Hey Peter/Valentin > > Are we waiting for any more feedback/testing for this? > I'm not overly fond of that last one, but AFAICT the only alternative is doing a full-fledged NUMA topology rebuild on new-node onlining (i.e. make calling sched_init_numa() more than once work). It's a lot more work for a very particular usecase. > > -- > Thanks and Regards > Srikar Dronamraju
diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c index b77ad49dc14f..f25dbcab4fd2 100644 --- a/kernel/sched/topology.c +++ b/kernel/sched/topology.c @@ -1833,6 +1833,9 @@ void sched_init_numa(void) sched_domains_numa_masks[i][j] = mask; for_each_node(k) { + if (!node_online(j)) + continue; + if (sched_debug() && (node_distance(j, k) != node_distance(k, j))) sched_numa_warn("Node-distance not symmetric"); @@ -1891,12 +1894,30 @@ void sched_init_numa(void) void sched_domains_numa_masks_set(unsigned int cpu) { int node = cpu_to_node(cpu); - int i, j; + int i, j, empty; + empty = cpumask_empty(sched_domains_numa_masks[0][node]); for (i = 0; i < sched_domains_numa_levels; i++) { for (j = 0; j < nr_node_ids; j++) { - if (node_distance(j, node) <= sched_domains_numa_distance[i]) + if (!node_online(j)) + continue; + + if (node_distance(j, node) <= sched_domains_numa_distance[i]) { cpumask_set_cpu(cpu, sched_domains_numa_masks[i][j]); + + /* + * We skip updating numa_masks for offline + * nodes. However now that the node is + * finally online, CPUs that were added + * earlier, should now be accommodated into + * newly oneline node's numa mask. + */ + if (node != j && empty) { + cpumask_or(sched_domains_numa_masks[i][node], + sched_domains_numa_masks[i][node], + sched_domains_numa_masks[0][j]); + } + } } } }
Currently scheduler doesn't check if node is online before adding CPUs to the node mask. However on some architectures, node distance is only available for nodes that are online. Its not sure how much to rely on the node distance, when one of the nodes is offline. If said node distance is fake (since one of the nodes is offline) and the actual node distance is different, then the cpumask of such nodes when the nodes become becomes online will be wrong. This can cause topology_span_sane to throw up a warning message and the rest of the topology being not updated properly. Resolve this by skipping update of cpumask for nodes that are not online. However by skipping, relevant CPUs may not be set when nodes are onlined. i.e when coming up with NUMA masks at a certain NUMA distance, CPUs that are part of other nodes, which are already online will not be part of the NUMA mask. Hence the first time, a CPU is added to the newly onlined node, add the other CPUs to the numa_mask. Cc: LKML <linux-kernel@vger.kernel.org> Cc: linuxppc-dev@lists.ozlabs.org Cc: Nathan Lynch <nathanl@linux.ibm.com> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Valentin Schneider <valentin.schneider@arm.com> Cc: Gautham R Shenoy <ego@linux.vnet.ibm.com> Cc: Dietmar Eggemann <dietmar.eggemann@arm.com> Cc: Mel Gorman <mgorman@techsingularity.net> Cc: Vincent Guittot <vincent.guittot@linaro.org> Cc: Rik van Riel <riel@surriel.com> Cc: Geetika Moolchandani <Geetika.Moolchandani1@ibm.com> Cc: Laurent Dufour <ldufour@linux.ibm.com> Reported-by: Geetika Moolchandani <Geetika.Moolchandani1@ibm.com> Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> --- Changelog v1->v2: v1 link: http://lore.kernel.org/lkml/20210520154427.1041031-4-srikar@linux.vnet.ibm.com/t/#u Update the NUMA masks, whenever 1st CPU is added to cpuless node kernel/sched/topology.c | 25 +++++++++++++++++++++++-- 1 file changed, 23 insertions(+), 2 deletions(-)