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Wed, 16 Sep 2020 08:22:04 +0000 (GMT) Received: from pomme.local (unknown [9.145.183.110]) by d06av25.portsmouth.uk.ibm.com (Postfix) with ESMTP; Wed, 16 Sep 2020 08:22:03 +0000 (GMT) Subject: Re: [PATCH v3] pseries/hotplug-memory: hot-add: skip redundant LMB lookup To: Scott Cheloha , linuxppc-dev@ozlabs.org References: <20200915194647.3334645-1-cheloha@linux.ibm.com> From: Laurent Dufour Message-ID: Date: Wed, 16 Sep 2020 10:22:03 +0200 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:68.0) Gecko/20100101 Thunderbird/68.12.0 MIME-Version: 1.0 In-Reply-To: <20200915194647.3334645-1-cheloha@linux.ibm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit 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_02:2020-09-15, 2020-09-16 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 phishscore=0 malwarescore=0 priorityscore=1501 adultscore=0 bulkscore=0 spamscore=0 clxscore=1015 mlxscore=0 impostorscore=0 suspectscore=0 mlxlogscore=999 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2009160054 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 , David Hildenbrand , Rick Lindsley Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Le 15/09/2020 à 21:46, Scott Cheloha a écrit : > 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 > --- > 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. > > 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..d15d9999bad6 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; > +extern int of_drconf_to_nid_single(struct drmem_lmb *); Hi Scott, checkpatch.pl reports: CHECK: extern prototypes should be avoided in .h files #106: FILE: arch/powerpc/include/asm/topology.h:90: +extern int of_drconf_to_nid_single(struct drmem_lmb *); WARNING: function definition argument 'struct drmem_lmb *' should also have an identifier name #106: FILE: arch/powerpc/include/asm/topology.h:90: +extern int of_drconf_to_nid_single(struct drmem_lmb *); cheers, Laurent. > + > #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); >