From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 49177ECE596 for ; Fri, 11 Oct 2019 03:00:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 29CF0214E0 for ; Fri, 11 Oct 2019 03:00:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726686AbfJKC76 (ORCPT ); Thu, 10 Oct 2019 22:59:58 -0400 Received: from mga14.intel.com ([192.55.52.115]:60510 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726116AbfJKC76 (ORCPT ); Thu, 10 Oct 2019 22:59:58 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by fmsmga103.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 10 Oct 2019 19:59:20 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.67,282,1566889200"; d="scan'208";a="219252094" Received: from richard.sh.intel.com (HELO localhost) ([10.239.159.54]) by fmsmga004.fm.intel.com with ESMTP; 10 Oct 2019 19:59:14 -0700 From: Wei Yang To: akpm@linux-foundation.org, kirill.shutemov@linux.intel.com, jglisse@redhat.com, mike.kravetz@oracle.com, riel@surriel.com, khlebnikov@yandex-team.ru, cai@lca.pw, shakeelb@google.com Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Wei Yang Subject: [Patch v3 2/2] mm/rmap.c: reuse mergeable anon_vma as parent when fork Date: Fri, 11 Oct 2019 10:58:41 +0800 Message-Id: <20191011025841.16801-2-richardw.yang@linux.intel.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20191011025841.16801-1-richardw.yang@linux.intel.com> References: <20191011025841.16801-1-richardw.yang@linux.intel.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org In function __anon_vma_prepare(), we will try to find anon_vma if it is possible to reuse it. While on fork, the logic is different. Since commit 5beb49305251 ("mm: change anon_vma linking to fix multi-process server scalability issue"), function anon_vma_clone() tries to allocate new anon_vma for child process. But the logic here will allocate a new anon_vma for each vma, even in parent this vma is mergeable and share the same anon_vma with its sibling. This may do better for scalability issue, while it is not necessary to do so especially after interval tree is used. Commit 7a3ef208e662 ("mm: prevent endless growth of anon_vma hierarchy") tries to reuse some anon_vma by counting child anon_vma and attached vmas. While for those mergeable anon_vmas, we can just reuse it and not necessary to go through the logic. After this change, kernel build test reduces 20% anon_vma allocation. Do the same kernel build test, it shows run time in sys reduced 11.5%. Origin: real 2m50.467s user 17m52.002s sys 1m51.953s real 2m48.662s user 17m55.464s sys 1m50.553s real 2m51.143s user 17m59.687s sys 1m53.600s Patched: real 2m40.080s user 17m4.644s sys 1m39.321s real 2m39.967s user 17m2.445s sys 1m38.850s real 2m40.581s user 17m1.975s sys 1m39.065s Signed-off-by: Wei Yang --- mm/rmap.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/mm/rmap.c b/mm/rmap.c index fc0aba7fb9b9..0dd5f8b04a48 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -269,6 +269,18 @@ int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src) struct anon_vma_chain *avc, *pavc; struct anon_vma *root = NULL; bool reuse = !dst->anon_vma && src->anon_vma; + struct vm_area_struct *prev = dst->vm_prev, *pprev = src->vm_prev; + + /* + * If parent share anon_vma with its vm_prev, keep this sharing in in + * child. + * + * 1. Parent has vm_prev, which implies we have vm_prev. + * 2. Parent and its vm_prev have the same anon_vma. + */ + if (reuse && pprev && pprev->anon_vma == src->anon_vma) + dst->anon_vma = prev->anon_vma; + list_for_each_entry_reverse(pavc, &src->anon_vma_chain, same_vma) { struct anon_vma *anon_vma; -- 2.17.1