From nobody Fri Oct 3 10:15:09 2025 Received: from mta22.hihonor.com (mta22.hihonor.com [81.70.192.198]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E2890221DB0 for ; Wed, 3 Sep 2025 09:27:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=81.70.192.198 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756891658; cv=none; b=hgpWznWvjaUWegR+r3jUID7+OMwNXORnbT3sdk1FpgxYpehoc2xWUG5EdQgBVMm+v3+Bjk52q8OFx+RhemVtA+8NHJHp6H2wrDypaKyXF5GC6dOhLOZC9sDkQ9GQf+Dv5TDyUmAJsHkhVh+LL4c9c7zQrjT3lbqS2RmkobQG7q0= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756891658; c=relaxed/simple; bh=qgbsyweIz0AfflDUBDRZEvg2PL8Y2IvPqdgBGb0n6Zw=; h=From:To:CC:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=s8+ZqVExQA73WPUL4K9xAm1qJeZhyvGGvBYqFBmk/grWMljuut0fEf+CJMISR46OBRN67JwZmlAT3fK0tCp7JKyqh/Ii1H7LDH8un3shkJlHtccI0SGhlHY7CAqVPkL7GtpMM+Ag17NJaJRvdKAKMHwZQlZSt/Ey/nbh64jkuWs= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=honor.com; spf=pass smtp.mailfrom=honor.com; dkim=pass (1024-bit key) header.d=honor.com header.i=@honor.com header.b=cQw7X1Jq; arc=none smtp.client-ip=81.70.192.198 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=honor.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=honor.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=honor.com header.i=@honor.com header.b="cQw7X1Jq" dkim-signature: v=1; a=rsa-sha256; d=honor.com; s=dkim; c=relaxed/relaxed; q=dns/txt; h=To:From; bh=r/uDUbzgtgsxWzj8Cop4+zLnEzwH2RYL27BPHIa6ZCs=; b=cQw7X1Jq2Xu+J4D6Zyt/8T0P6nCWF3oej7qVCUJgXulRFneyvMt5DR7J9q1t7nYhpz2Wm9EBP 6gG0WS87WbWdNEYsQyIc42Zg052Z5ZThHtm32MGNDnQxj1RmzoeYVNKu1otjb8W4WmimcZcD/7+ Cq7kReGDau7TK7hFwkUtTM8= Received: from w012.hihonor.com (unknown [10.68.27.189]) by mta22.hihonor.com (SkyGuard) with ESMTPS id 4cGy1g4kKqzYnw7d; Wed, 3 Sep 2025 17:27:19 +0800 (CST) Received: from a018.hihonor.com (10.68.17.250) by w012.hihonor.com (10.68.27.189) 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 17:27:34 +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> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-ClientProxiedBy: w003.hihonor.com (10.68.17.88) To a018.hihonor.com (10.68.17.250) Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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: Michal Hocko Acked-by: Shakeel Butt --- 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 =3D true; - VMA_ITERATOR(vmi, mm, 0); + MA_STATE(mas, &mm->mm_mt, ULONG_MAX, ULONG_MAX); =20 /* * 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); =20 - 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; =20 --=20 2.17.1