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From: Roman Gushchin To: Shakeel Butt Cc: Andrew Morton , Johannes Weiner , Michal Hocko , Muchun Song , Yosry Ahmed , ying.huang@intel.com, feng.tang@intel.com, fengwei.yin@intel.com, oliver.sang@intel.com, kernel-team@meta.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] memcg: rearrage fields of mem_cgroup_per_node Message-ID: References: <20240523034824.1255719-1-shakeel.butt@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240523034824.1255719-1-shakeel.butt@linux.dev> X-Migadu-Flow: FLOW_OUT X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: D404D40002 X-Stat-Signature: 8w175nsha4kgppfrg4byu44jeeh1dpec X-HE-Tag: 1716478456-329388 X-HE-Meta: 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 r6iQEd5H /gpC5K+iR8k4Yz62qYD9w3JfYsaAKvAlrlL35g5bME2kZG0yZTdu5GNetR007bhCf1ov57Nsy7Dmml7cNf5i+h4gqdmX4Ah4tKZD2pccf8xfIvI+7GCwF9plsvzIOY9C0xZ35Wa8Mhr+In4jM5xZ78kkFTLE5xTySWyNfWvxkfrmCeCdPdwexit3LsvrWuyA3PmuK1u9b/73JyANDF5xaXoV4J6LZ3morOUCIOO5ArFpy6gASh2379JZPrxBVCgV3rh4dZHc97CrhkgU= 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: List-Subscribe: List-Unsubscribe: On Wed, May 22, 2024 at 08:48:24PM -0700, Shakeel Butt wrote: > Kernel test robot reported [1] performance regression for will-it-scale > test suite's page_fault2 test case for the commit 70a64b7919cb ("memcg: > dynamically allocate lruvec_stats"). After inspection it seems like the > commit has unintentionally introduced false cache sharing. > > After the commit the fields of mem_cgroup_per_node which get read on the > performance critical path share the cacheline with the fields which > get updated often on LRU page allocations or deallocations. This has > caused contention on that cacheline and the workloads which manipulates > a lot of LRU pages are regressed as reported by the test report. > > The solution is to rearrange the fields of mem_cgroup_per_node such that > the false sharing is eliminated. Let's move all the read only pointers > at the start of the struct, followed by memcg-v1 only fields and at the > end fields which get updated often. > > Experiment setup: Ran fallocate1, fallocate2, page_fault1, page_fault2 > and page_fault3 from the will-it-scale test suite inside a three level > memcg with /tmp mounted as tmpfs on two different machines, one a single > numa node and the other one, two node machine. > > $ ./[testcase]_processes -t $NR_CPUS -s 50 > > Results for single node, 52 CPU machine: > > Testcase base with-patch > > fallocate1 1031081 1431291 (38.80 %) > fallocate2 1029993 1421421 (38.00 %) > page_fault1 2269440 3405788 (50.07 %) > page_fault2 2375799 3572868 (50.30 %) > page_fault3 28641143 28673950 ( 0.11 %) > > Results for dual node, 80 CPU machine: > > Testcase base with-patch > > fallocate1 2976288 3641185 (22.33 %) > fallocate2 2979366 3638181 (22.11 %) > page_fault1 6221790 7748245 (24.53 %) > page_fault2 6482854 7847698 (21.05 %) > page_fault3 28804324 28991870 ( 0.65 %) > > Fixes: 70a64b7919cb ("memcg: dynamically allocate lruvec_stats") > Reported-by: kernel test robot > Closes: https://lore.kernel.org/oe-lkp/202405171353.b56b845-oliver.sang@intel.com > Signed-off-by: Shakeel Butt Reviewed-by: Roman Gushchin Thanks!