| Message ID | 20231016124305.139923-1-npiggin@gmail.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | powerpc/qspinlock: Fix yield latency bug and other | expand |
On 10/16/23 6:12 PM, Nicholas Piggin wrote: > This fixes a long-standing latency bug in the powerpc qspinlock > implementation that quite a few people have reported and helped > out with debugging. > > The first patch is a minimal fix that avoids the problem. The > other patches are streamlining and improvements after the fix. > Hi Nick, Thanks for the fix. This issue has been happening in various scenarios when there was vCPU contention. Tested this on Power10 Shared processor LPAR(SPLPAR) based on powerVM. System has two SPLPARs. on LPAR1 trying various scenarios and LPAR2 is running constant stress-ng threads consuming 100% its CPU. LPAR1: 96VP, 64EC and LPAR2 is 32VP, 32EC. lscpu of LPAR1: Architecture: ppc64le Byte Order: Little Endian CPU(s): 768 On-line CPU(s) list: 0-767 Model name: POWER10 (architected), altivec supported Model: 2.0 (pvr 0080 0200) Thread(s) per core: 8 Scenarios tried on LPAR1: 1. run ppc64_cpu --smt=1 and ppc64_cpu --smt=8 to switch between SMT=1 and SMT=8 2. create a cgroup, assign 5% quota to it and run same number of stress-ng as number of CPUs within that cgroup. 3. Run a suite of microbenchmarks such as unixbench, schbench, hackbench stress-ng with perf enabled. baseline was tip/master at 84ab57184ff4 (origin/master, origin/HEAD) Merge branch into tip/master: 'x86/tdx' Hard lockup was SEEN in each of the above scenario with baseline. With this patch series applied hard lockup was NOT SEEN in each of the above scenario. So, Tested-by: Shrikanth Hegde <sshegde@linux.vnet.ibm.com> > Thanks, > Nick > > Nicholas Piggin (6): > powerpc/qspinlock: Fix stale propagated yield_cpu > powerpc/qspinlock: stop queued waiters trying to set lock sleepy > powerpc/qspinlock: propagate owner preemptedness rather than CPU > number > powerpc/qspinlock: don't propagate the not-sleepy state > powerpc/qspinlock: Propagate sleepy if previous waiter is preempted > powerpc/qspinlock: Rename yield_propagate_owner tunable > > arch/powerpc/lib/qspinlock.c | 119 +++++++++++++++-------------------- > 1 file changed, 52 insertions(+), 67 deletions(-) >
On Mon, Oct 16, 2023 at 10:42:59PM +1000, Nicholas Piggin wrote: > This fixes a long-standing latency bug in the powerpc qspinlock > implementation that quite a few people have reported and helped > out with debugging. > > The first patch is a minimal fix that avoids the problem. The > other patches are streamlining and improvements after the fix. > > Thanks, > Nick > > Nicholas Piggin (6): > powerpc/qspinlock: Fix stale propagated yield_cpu > powerpc/qspinlock: stop queued waiters trying to set lock sleepy > powerpc/qspinlock: propagate owner preemptedness rather than CPU > number > powerpc/qspinlock: don't propagate the not-sleepy state > powerpc/qspinlock: Propagate sleepy if previous waiter is preempted > powerpc/qspinlock: Rename yield_propagate_owner tunable > > arch/powerpc/lib/qspinlock.c | 119 +++++++++++++++-------------------- > 1 file changed, 52 insertions(+), 67 deletions(-) > > -- > 2.42.0 > Just a minor comment regarding patch 2. For the series: Reviewed-by: Nysal Jan K.A <nysal@linux.ibm.com>
On Mon, 16 Oct 2023 22:42:59 +1000, Nicholas Piggin wrote: > This fixes a long-standing latency bug in the powerpc qspinlock > implementation that quite a few people have reported and helped > out with debugging. > > The first patch is a minimal fix that avoids the problem. The > other patches are streamlining and improvements after the fix. > > [...] Patch 1 applied to powerpc/fixes. [1/6] powerpc/qspinlock: Fix stale propagated yield_cpu https://git.kernel.org/powerpc/c/f9bc9bbe8afdf83412728f0b464979a72a3b9ec2 cheers
On Mon, 16 Oct 2023 22:42:59 +1000, Nicholas Piggin wrote: > This fixes a long-standing latency bug in the powerpc qspinlock > implementation that quite a few people have reported and helped > out with debugging. > > The first patch is a minimal fix that avoids the problem. The > other patches are streamlining and improvements after the fix. > > [...] Applied to powerpc/next. [2/6] powerpc/qspinlock: stop queued waiters trying to set lock sleepy https://git.kernel.org/powerpc/c/f6568647382c667912245c8d07aa26c9c6d4d0c8 [3/6] powerpc/qspinlock: propagate owner preemptedness rather than CPU number https://git.kernel.org/powerpc/c/fd8fae50c9c6117c4e05954deab2cc515508666b [4/6] powerpc/qspinlock: don't propagate the not-sleepy state https://git.kernel.org/powerpc/c/fcf77d44274b96a55cc74043561a4b3151b9ad24 [5/6] powerpc/qspinlock: Propagate sleepy if previous waiter is preempted https://git.kernel.org/powerpc/c/1e6d5f725738fff83e1c3cbdb8547142eb8820c2 [6/6] powerpc/qspinlock: Rename yield_propagate_owner tunable https://git.kernel.org/powerpc/c/b629b541702b082d161c307c9d7d9867911fc933 cheers
This fixes a long-standing latency bug in the powerpc qspinlock implementation that quite a few people have reported and helped out with debugging. The first patch is a minimal fix that avoids the problem. The other patches are streamlining and improvements after the fix. Thanks, Nick Nicholas Piggin (6): powerpc/qspinlock: Fix stale propagated yield_cpu powerpc/qspinlock: stop queued waiters trying to set lock sleepy powerpc/qspinlock: propagate owner preemptedness rather than CPU number powerpc/qspinlock: don't propagate the not-sleepy state powerpc/qspinlock: Propagate sleepy if previous waiter is preempted powerpc/qspinlock: Rename yield_propagate_owner tunable arch/powerpc/lib/qspinlock.c | 119 +++++++++++++++-------------------- 1 file changed, 52 insertions(+), 67 deletions(-)