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Wed, 3 Sep 2025 17:27:34 +0800 Received: from localhost.localdomain (10.144.20.219) by a018.hihonor.com (10.68.17.250) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Wed, 3 Sep 2025 17:27:33 +0800 From: zhongjinji To: CC: , , , , , , , , , , , Subject: [PATCH v7 2/2] mm/oom_kill: The OOM reaper traverses the VMA maple tree in reverse order Date: Wed, 3 Sep 2025 17:27:29 +0800 Message-ID: <20250903092729.10611-3-zhongjinji@honor.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20250903092729.10611-1-zhongjinji@honor.com> References: <20250903092729.10611-1-zhongjinji@honor.com> MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [10.144.20.219] X-ClientProxiedBy: w003.hihonor.com (10.68.17.88) To a018.hihonor.com (10.68.17.250) X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: B60F2100007 X-Stat-Signature: ifbdcfhqrs5bd31djkua1a76mjb7ky41 X-Rspam-User: X-HE-Tag: 1756891658-339862 X-HE-Meta: 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 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: 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 --- mm/oom_kill.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/mm/oom_kill.c b/mm/oom_kill.c index 3caaafc896d4..540b1e5e0e46 100644 --- a/mm/oom_kill.c +++ b/mm/oom_kill.c @@ -516,7 +516,7 @@ static bool __oom_reap_task_mm(struct mm_struct *mm) { struct vm_area_struct *vma; bool ret = true; - VMA_ITERATOR(vmi, mm, 0); + MA_STATE(mas, &mm->mm_mt, ULONG_MAX, ULONG_MAX); /* * Tell all users of get_user/copy_from_user etc... that the content @@ -526,7 +526,13 @@ static bool __oom_reap_task_mm(struct mm_struct *mm) */ set_bit(MMF_UNSTABLE, &mm->flags); - for_each_vma(vmi, vma) { + /* + * It 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. + */ + mas_for_each_rev(&mas, vma, 0) { if (vma->vm_flags & (VM_HUGETLB|VM_PFNMAP)) continue; -- 2.17.1