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Mon, 17 Aug 2026 17:54:17 +0000 X-Migadu-Flow: FLOW_OUT Date: Mon, 17 Aug 2026 10:54:16 -0700 From: Shakeel Butt To: Andrew Morton Cc: Usama Arif , cgroups@vger.kernel.org, hannes@cmpxchg.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, mhocko@kernel.org, muchun.song@linux.dev, roman.gushchin@linux.dev, david@kernel.org, kernel-team@meta.com, kernel test robot Subject: Re: [PATCH] mm/memcontrol: avoid false sharing between vmstats and events Message-ID: References: <20260817103835.2937733-1-usama.arif@linux.dev> <20260817104340.c9bd2dae70d4fa31fd66b216@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260817104340.c9bd2dae70d4fa31fd66b216@linux-foundation.org> X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 1680440004 X-Stat-Signature: mfdbkwkomjy8fxqtc86zimhzuutczct6 X-Rspam-User: X-HE-Tag: 1786989258-425359 X-HE-Meta: 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 Xp6fFKAi 39N0FKPJk+leUwYbUD/UeB9Bq71UYwHTap5V2Jv5qHRo7a9Qfx+oU6cDXM7iTmRFruf7GqXkW5NOoZSeGI++Ay9ulJf/SQQVLrID3NNQkhL8gu5YO5v0cIi/nwQ/vR/5hr1cvjQ17j0WZfN46i+ZACwG87udEaqkEyypEwbUCjpywE83V/b1bXxVnu+5JBxgsx7R2niuFwiAkKFnF3J2kUXn84qmncpY+vkj3QYsQ3dizXjBk1+dBkK/kBKBNKiPLTV/MFwUTDs8zFw3hocQdIC0LUF1JUbqTGbeHq183A8X7vMqsrivIABAYKX0tLLHzoCYszo1ic1xklnDgdMhFHXGfvZcjjp+6oKlGBqKS+za1cBngXtMF9dBgyg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Aug 17, 2026 at 10:43:40AM -0700, Andrew Morton wrote: > On Mon, 17 Aug 2026 03:38:35 -0700 Usama Arif wrote: > > > Moving v1 userspace eventfd handling into memcontrol-v1.c shrank > > struct vmpressure from 112 to 24 bytes when CONFIG_MEMCG_V1 is disabled. > > This moved memory_events_local[MEMCG_SWAP_FAIL] and the hot > > vmstats_percpu pointer onto the same cacheline. > > > > The stress-ng mremap stressor exercises MADV_PAGEOUT with swap > > disabled, generating about 20 million MEMCG_SWAP_FAIL updates per > > 60-second run on a 176-CPU test system. Those writes bounce the line > > while memcg statistics paths load vmstats_percpu. > > > > Move cgwb_list into the existing alignment gap and cacheline-align > > vmstats_percpu. This separates the pointer from the event counters > > without increasing the size of struct mem_cgroup in the tested > > configuration. > > > > The blamed commit reduced median mremap throughput by 4.38% on the > > test system with one socket. The patched kernel brings the performance > > to within 0.5% of the parent which is within the observed boot-to-boot > > spread (up to 1.2%). > > Cool, thanks. > > > Fixes: ea928e9e18da ("mm/vmpressure: move v1 userspace eventfd code into memcontrol-v1.c") > > That's in mm-stable so I'll squeeze this fix into next week's 7.3-rc1 > merge pile. Thanks Andrew. We should also add the following tag due to http://lore.kernel.org/aoAABX59IzUXz/Rv@ly-workstation Tested-by: kernel test robot > >