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Wed, 16 Sep 2020 14:51:22 +0000 (GMT) Received: from rascal.austin.ibm.com (unknown [9.41.179.32]) by b03ledav001.gho.boulder.ibm.com (Postfix) with ESMTP; Wed, 16 Sep 2020 14:51:22 +0000 (GMT) From: Scott Cheloha To: linuxppc-dev@ozlabs.org Subject: [PATCH v4] pseries/hotplug-memory: hot-add: skip redundant LMB lookup Date: Wed, 16 Sep 2020 09:51:22 -0500 Message-Id: <20200916145122.3408129-1-cheloha@linux.ibm.com> X-Mailer: git-send-email 2.24.1 MIME-Version: 1.0 X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.235, 18.0.687 definitions=2020-09-16_07:2020-09-16, 2020-09-16 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 suspectscore=0 impostorscore=0 priorityscore=1501 adultscore=0 malwarescore=0 phishscore=0 mlxlogscore=999 spamscore=0 mlxscore=0 bulkscore=0 clxscore=1015 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2009160106 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Nathan Lynch , Michal Suchanek , Laurent Dufour , David Hildenbrand , Rick Lindsley Errors-To: linuxppc-dev-bounces+patchwork-incoming=ozlabs.org@lists.ozlabs.org Sender: "Linuxppc-dev" During memory hot-add, dlpar_add_lmb() calls memory_add_physaddr_to_nid() to determine which node id (nid) to use when later calling __add_memory(). This is wasteful. On pseries, memory_add_physaddr_to_nid() finds an appropriate nid for a given address by looking up the LMB containing the address and then passing that LMB to of_drconf_to_nid_single() to get the nid. In dlpar_add_lmb() we get this address from the LMB itself. In short, we have a pointer to an LMB and then we are searching for that LMB *again* in order to find its nid. If we call of_drconf_to_nid_single() directly from dlpar_add_lmb() we can skip the redundant lookup. The only error handling we need to duplicate from memory_add_physaddr_to_nid() is the fallback to the default nid when drconf_to_nid_single() returns -1 (NUMA_NO_NODE) or an invalid nid. Skipping the extra lookup makes hot-add operations faster, especially on machines with many LMBs. Consider an LPAR with 126976 LMBs. In one test, hot-adding 126000 LMBs on an upatched kernel took ~3.5 hours while a patched kernel completed the same operation in ~2 hours: Unpatched (12450 seconds): Sep 9 04:06:31 ltc-brazos1 drmgr[810169]: drmgr: -c mem -a -q 126000 Sep 9 04:06:31 ltc-brazos1 kernel: pseries-hotplug-mem: Attempting to hot-add 126000 LMB(s) [...] Sep 9 07:34:01 ltc-brazos1 kernel: pseries-hotplug-mem: Memory at 20000000 (drc index 80000002) was hot-added Patched (7065 seconds): Sep 8 21:49:57 ltc-brazos1 drmgr[877703]: drmgr: -c mem -a -q 126000 Sep 8 21:49:57 ltc-brazos1 kernel: pseries-hotplug-mem: Attempting to hot-add 126000 LMB(s) [...] Sep 8 23:27:42 ltc-brazos1 kernel: pseries-hotplug-mem: Memory at 20000000 (drc index 80000002) was hot-added It should be noted that the speedup grows more substantial when hot-adding LMBs at the end of the drconf range. This is because we are skipping a linear LMB search. To see the distinction, consider smaller hot-add test on the same LPAR. A perf-stat run with 10 iterations showed that hot-adding 4096 LMBs completed less than 1 second faster on a patched kernel: Unpatched: Performance counter stats for 'drmgr -c mem -a -q 4096' (10 runs): 104,753.42 msec task-clock # 0.992 CPUs utilized ( +- 0.55% ) 4,708 context-switches # 0.045 K/sec ( +- 0.69% ) 2,444 cpu-migrations # 0.023 K/sec ( +- 1.25% ) 394 page-faults # 0.004 K/sec ( +- 0.22% ) 445,902,503,057 cycles # 4.257 GHz ( +- 0.55% ) (66.67%) 8,558,376,740 stalled-cycles-frontend # 1.92% frontend cycles idle ( +- 0.88% ) (49.99%) 300,346,181,651 stalled-cycles-backend # 67.36% backend cycles idle ( +- 0.76% ) (50.01%) 258,091,488,691 instructions # 0.58 insn per cycle # 1.16 stalled cycles per insn ( +- 0.22% ) (66.67%) 70,568,169,256 branches # 673.660 M/sec ( +- 0.17% ) (50.01%) 3,100,725,426 branch-misses # 4.39% of all branches ( +- 0.20% ) (49.99%) 105.583 +- 0.589 seconds time elapsed ( +- 0.56% ) Patched: Performance counter stats for 'drmgr -c mem -a -q 4096' (10 runs): 104,055.69 msec task-clock # 0.993 CPUs utilized ( +- 0.32% ) 4,606 context-switches # 0.044 K/sec ( +- 0.20% ) 2,463 cpu-migrations # 0.024 K/sec ( +- 0.93% ) 394 page-faults # 0.004 K/sec ( +- 0.25% ) 442,951,129,921 cycles # 4.257 GHz ( +- 0.32% ) (66.66%) 8,710,413,329 stalled-cycles-frontend # 1.97% frontend cycles idle ( +- 0.47% ) (50.06%) 299,656,905,836 stalled-cycles-backend # 67.65% backend cycles idle ( +- 0.39% ) (50.02%) 252,731,168,193 instructions # 0.57 insn per cycle # 1.19 stalled cycles per insn ( +- 0.20% ) (66.66%) 68,902,851,121 branches # 662.173 M/sec ( +- 0.13% ) (49.94%) 3,100,242,882 branch-misses # 4.50% of all branches ( +- 0.15% ) (49.98%) 104.829 +- 0.325 seconds time elapsed ( +- 0.31% ) This is consistent. An add-by-count hot-add operation adds LMBs greedily, so LMBs near the start of the drconf range are considered first. On an otherwise idle LPAR with so many LMBs we would expect to find the LMBs we need near the start of the drconf range, hence the smaller speedup. Signed-off-by: Scott Cheloha Reviewed-by: Laurent Dufour --- Changelog: v1: https://lore.kernel.org/linuxppc-dev/20200910175637.2865160-1-cheloha@linux.ibm.com/ v2: - Move prototype for of_drconf_to_nid_single() to topology.h. Requested by Michael Ellerman. v3: - Send the right patch. v2 is from the wrong branch, my mistake. v4: - Fix checkpatch.pl warnings. Reported by Laurent Dufour. arch/powerpc/include/asm/topology.h | 3 +++ arch/powerpc/mm/numa.c | 2 +- arch/powerpc/platforms/pseries/hotplug-memory.c | 6 ++++-- 3 files changed, 8 insertions(+), 3 deletions(-) diff --git a/arch/powerpc/include/asm/topology.h b/arch/powerpc/include/asm/topology.h index f0b6300e7dd3..ae19b19f9d44 100644 --- a/arch/powerpc/include/asm/topology.h +++ b/arch/powerpc/include/asm/topology.h @@ -86,6 +86,9 @@ static inline int cpu_distance(__be32 *cpu1_assoc, __be32 *cpu2_assoc) #endif /* CONFIG_NUMA */ +struct drmem_lmb; +int of_drconf_to_nid_single(struct drmem_lmb *lmb); + #if defined(CONFIG_NUMA) && defined(CONFIG_PPC_SPLPAR) extern int find_and_online_cpu_nid(int cpu); #else diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c index 1f61fa2148b5..63507b47164d 100644 --- a/arch/powerpc/mm/numa.c +++ b/arch/powerpc/mm/numa.c @@ -430,7 +430,7 @@ static int of_get_assoc_arrays(struct assoc_arrays *aa) * This is like of_node_to_nid_single() for memory represented in the * ibm,dynamic-reconfiguration-memory node. */ -static int of_drconf_to_nid_single(struct drmem_lmb *lmb) +int of_drconf_to_nid_single(struct drmem_lmb *lmb) { struct assoc_arrays aa = { .arrays = NULL }; int default_nid = NUMA_NO_NODE; diff --git a/arch/powerpc/platforms/pseries/hotplug-memory.c b/arch/powerpc/platforms/pseries/hotplug-memory.c index 0ea976d1cac4..9a533acf8ad0 100644 --- a/arch/powerpc/platforms/pseries/hotplug-memory.c +++ b/arch/powerpc/platforms/pseries/hotplug-memory.c @@ -611,8 +611,10 @@ static int dlpar_add_lmb(struct drmem_lmb *lmb) block_sz = memory_block_size_bytes(); - /* Find the node id for this address. */ - nid = memory_add_physaddr_to_nid(lmb->base_addr); + /* Find the node id for this LMB. Fake one if necessary. */ + nid = of_drconf_to_nid_single(lmb); + if (nid < 0 || !node_possible(nid)) + nid = first_online_node; /* Add the memory */ rc = __add_memory(nid, lmb->base_addr, block_sz);