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From: Shakeel Butt To: zhongjinji Cc: mhocko@suse.com, rientjes@google.com, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, tglx@linutronix.de, liam.howlett@oracle.com, lorenzo.stoakes@oracle.com, surenb@google.com, liulu.liu@honor.com, feng.han@honor.com Subject: Re: [PATCH v7 2/2] mm/oom_kill: The OOM reaper traverses the VMA maple tree in reverse order Message-ID: References: <20250903092729.10611-1-zhongjinji@honor.com> <20250903092729.10611-3-zhongjinji@honor.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250903092729.10611-3-zhongjinji@honor.com> X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 586DC4000B X-Stat-Signature: g7yxkq5diwabrwksudha6i9gm6akbdng X-Rspam-User: X-HE-Tag: 1757029827-591900 X-HE-Meta: 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 jRhGBR9h XDFGUAp6OhNno4OSuzFmHume/SAJzgDsml/8qYX0KA5JVysx//fS/oN3HDC60i7Vlw+37W/W6nkgYtxcI04xre/vlaTEvvMExwzC6yDcTwSzSx2z6Tz+9MHlZkGR4syW2sBBmXimsSm58zQMedvdA89/It4mgz3INjVa4Qk26jfmSmUgvmhim19LgSRXZUmmD0CokYUMIHUTerBUMTe5NevaP/dGIus81iEqfAx5IO+iQEh803UJBbz3Z111x1lUPCvli599L43KSh2oHtO7nWcba6eGjrfHuUNX05qizwotf2HalfKJIY7kG2NTpuhmX/yJx 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, Sep 03, 2025 at 05:27:29PM +0800, zhongjinji wrote: > Although the oom_reaper is delayed and it gives the oom victim chance to > clean up its address space this might take a while especially for > processes with a large address space footprint. In those cases > oom_reaper might start racing with the dying task and compete for shared > resources - e.g. page table lock contention has been observed. > > Reduce those races by reaping the oom victim from the other end of the > address space. > > It is also a significant improvement for process_mrelease(). When a process > is killed, process_mrelease is used to reap the killed process and often > runs concurrently with the dying task. The test data shows that after > applying the patch, lock contention is greatly reduced during the procedure > of reaping the killed process. > > Without the patch: > |--99.74%-- oom_reaper > | |--76.67%-- unmap_page_range > | | |--33.70%-- __pte_offset_map_lock > | | | |--98.46%-- _raw_spin_lock > | | |--27.61%-- free_swap_and_cache_nr > | | |--16.40%-- folio_remove_rmap_ptes > | | |--12.25%-- tlb_flush_mmu > | |--12.61%-- tlb_finish_mmu > > With the patch: > |--98.84%-- oom_reaper > | |--53.45%-- unmap_page_range > | | |--24.29%-- [hit in function] > | | |--48.06%-- folio_remove_rmap_ptes > | | |--17.99%-- tlb_flush_mmu > | | |--1.72%-- __pte_offset_map_lock > | |--30.43%-- tlb_finish_mmu > > Signed-off-by: zhongjinji Acked-by: Shakeel Butt