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27 Jun 2022 07:48:28 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.92,226,1650956400"; d="scan'208";a="679604256" Received: from shbuild999.sh.intel.com (HELO localhost) ([10.239.146.138]) by FMSMGA003.fm.intel.com with ESMTP; 27 Jun 2022 07:48:23 -0700 Date: Mon, 27 Jun 2022 22:48:22 +0800 From: Feng Tang To: Eric Dumazet Cc: Shakeel Butt , Linux MM , Andrew Morton , Roman Gushchin , Michal Hocko , Johannes Weiner , Muchun Song , Jakub Kicinski , Xin Long , Marcelo Ricardo Leitner , kernel test robot , Soheil Hassas Yeganeh , LKML , network dev , linux-s390@vger.kernel.org, MPTCP Upstream , "linux-sctp @ vger . kernel . org" , lkp@lists.01.org, kbuild test robot , Huang Ying , Xing Zhengjun , Yin Fengwei , Ying Xu Subject: Re: [net] 4890b686f4: netperf.Throughput_Mbps -69.4% regression Message-ID: <20220627144822.GA20878@shbuild999.sh.intel.com> References: <20220623185730.25b88096@kernel.org> <20220624070656.GE79500@shbuild999.sh.intel.com> <20220624144358.lqt2ffjdry6p5u4d@google.com> <20220625023642.GA40868@shbuild999.sh.intel.com> <20220627023812.GA29314@shbuild999.sh.intel.com> <20220627123415.GA32052@shbuild999.sh.intel.com> MIME-Version: 1.0 Content-Type: text/plain; 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spf=none (imf06.hostedemail.com: domain of feng.tang@intel.com has no SPF policy when checking 192.55.52.43) smtp.mailfrom=feng.tang@intel.com; dmarc=pass (policy=none) header.from=intel.com X-Rspam-User: Authentication-Results: imf06.hostedemail.com; dkim=pass header.d=intel.com header.s=Intel header.b=XCErenIJ; spf=none (imf06.hostedemail.com: domain of feng.tang@intel.com has no SPF policy when checking 192.55.52.43) smtp.mailfrom=feng.tang@intel.com; dmarc=pass (policy=none) header.from=intel.com X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 9D7B4180007 X-Stat-Signature: dgarjx7cjc5idctkjybm8wqeba7unohg X-HE-Tag: 1656341310-871635 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Jun 27, 2022 at 04:07:55PM +0200, Eric Dumazet wrote: > On Mon, Jun 27, 2022 at 2:34 PM Feng Tang wrote: > > > > On Mon, Jun 27, 2022 at 10:46:21AM +0200, Eric Dumazet wrote: > > > On Mon, Jun 27, 2022 at 4:38 AM Feng Tang wrote: > > [snip] > > > > > > > > > > > > Thanks Feng. Can you check the value of memory.kmem.tcp.max_usage_in_bytes > > > > > > in /sys/fs/cgroup/memory/system.slice/lkp-bootstrap.service after making > > > > > > sure that the netperf test has already run? > > > > > > > > > > memory.kmem.tcp.max_usage_in_bytes:0 > > > > > > > > Sorry, I made a mistake that in the original report from Oliver, it > > > > was 'cgroup v2' with a 'debian-11.1' rootfs. > > > > > > > > When you asked about cgroup info, I tried the job on another tbox, and > > > > the original 'job.yaml' didn't work, so I kept the 'netperf' test > > > > parameters and started a new job which somehow run with a 'debian-10.4' > > > > rootfs and acutally run with cgroup v1. > > > > > > > > And as you mentioned cgroup version does make a big difference, that > > > > with v1, the regression is reduced to 1% ~ 5% on different generations > > > > of test platforms. Eric mentioned they also got regression report, > > > > but much smaller one, maybe it's due to the cgroup version? > > > > > > This was using the current net-next tree. > > > Used recipe was something like: > > > > > > Make sure cgroup2 is mounted or mount it by mount -t cgroup2 none $MOUNT_POINT. > > > Enable memory controller by echo +memory > $MOUNT_POINT/cgroup.subtree_control. > > > Create a cgroup by mkdir $MOUNT_POINT/job. > > > Jump into that cgroup by echo $$ > $MOUNT_POINT/job/cgroup.procs. > > > > > > > > > > > > The regression was smaller than 1%, so considered noise compared to > > > the benefits of the bug fix. > > > > Yes, 1% is just around noise level for a microbenchmark. > > > > I went check the original test data of Oliver's report, the tests was > > run 6 rounds and the performance data is pretty stable (0Day's report > > will show any std deviation bigger than 2%) > > > > The test platform is a 4 sockets 72C/144T machine, and I run the > > same job (nr_tasks = 25% * nr_cpus) on one CascadeLake AP (4 nodes) > > and one Icelake 2 sockets platform, and saw 75% and 53% regresson on > > them. > > > > In the first email, there is a file named 'reproduce', it shows the > > basic test process: > > > > " > > use 'performane' cpufre governor for all CPUs > > > > netserver -4 -D > > modprobe sctp > > netperf -4 -H 127.0.0.1 -t SCTP_STREAM_MANY -c -C -l 300 -- -m 10K & > > netperf -4 -H 127.0.0.1 -t SCTP_STREAM_MANY -c -C -l 300 -- -m 10K & > > netperf -4 -H 127.0.0.1 -t SCTP_STREAM_MANY -c -C -l 300 -- -m 10K & > > (repeat 36 times in total) > > ... > > > > " > > > > Which starts 36 (25% of nr_cpus) netperf clients. And the clients number > > also matters, I tried to increase the client number from 36 to 72(50%), > > and the regression is changed from 69.4% to 73.7%" > > > > This seems like a lot of opportunities for memcg folks :) > > struct page_counter has poor field placement [1], and no per-cpu cache. > > [1] "atomic_long_t usage" is sharing cache line with read mostly fields. > > (struct mem_cgroup also has poor field placement, mainly because of > struct page_counter) > > 28.69% [kernel] [k] copy_user_enhanced_fast_string > 16.13% [kernel] [k] intel_idle_irq > 6.46% [kernel] [k] page_counter_try_charge > 6.20% [kernel] [k] __sk_mem_reduce_allocated > 5.68% [kernel] [k] try_charge_memcg > 5.16% [kernel] [k] page_counter_cancel Yes, I also analyzed the perf-profile data, and made some layout changes which could recover the changes from 69% to 40%. 7c80b038d23e1f4c 4890b686f4088c90432149bd6de 332b589c49656a45881bca4ecc0 ---------------- --------------------------- --------------------------- 15722 -69.5% 4792 -40.8% 9300 netperf.Throughput_Mbps diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h index 1bfcfb1af352..aa37bd39116c 100644 --- a/include/linux/cgroup-defs.h +++ b/include/linux/cgroup-defs.h @@ -179,14 +179,13 @@ struct cgroup_subsys_state { atomic_t online_cnt; /* percpu_ref killing and RCU release */ - struct work_struct destroy_work; struct rcu_work destroy_rwork; - + struct cgroup_subsys_state *parent; + struct work_struct destroy_work; /* * PI: the parent css. Placed here for cache proximity to following * fields of the containing structure. */ - struct cgroup_subsys_state *parent; }; /* diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index 9ecead1042b9..963b88ab9930 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -239,9 +239,6 @@ struct mem_cgroup { /* Private memcg ID. Used to ID objects that outlive the cgroup */ struct mem_cgroup_id id; - /* Accounted resources */ - struct page_counter memory; /* Both v1 & v2 */ - union { struct page_counter swap; /* v2 only */ struct page_counter memsw; /* v1 only */ @@ -251,6 +248,9 @@ struct mem_cgroup { struct page_counter kmem; /* v1 only */ struct page_counter tcpmem; /* v1 only */ + /* Accounted resources */ + struct page_counter memory; /* Both v1 & v2 */ + /* Range enforcement for interrupt charges */ struct work_struct high_work; @@ -313,7 +313,6 @@ struct mem_cgroup { atomic_long_t memory_events[MEMCG_NR_MEMORY_EVENTS]; atomic_long_t memory_events_local[MEMCG_NR_MEMORY_EVENTS]; - unsigned long socket_pressure; /* Legacy tcp memory accounting */ bool tcpmem_active; @@ -349,6 +348,7 @@ struct mem_cgroup { #ifdef CONFIG_TRANSPARENT_HUGEPAGE struct deferred_split deferred_split_queue; #endif + unsigned long socket_pressure; struct mem_cgroup_per_node *nodeinfo[]; }; And some of these are specific for network and may not be a universal win, though I think the 'cgroup_subsys_state' could keep the read-mostly 'parent' away from following written-mostly counters. Btw, I tried your debug patch which compiled fail with 0Day's kbuild system, but it did compile ok on my local machine. Thanks, Feng > > > Thanks, > > Feng > > > > > > > > > > Thanks, > > > > Feng