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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 C0A91C4360C for ; Fri, 4 Oct 2019 23:49:30 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 847C1215EA for ; Fri, 4 Oct 2019 23:49:30 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 847C1215EA Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 36EF06B0008; Fri, 4 Oct 2019 19:49:30 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 345906B000A; Fri, 4 Oct 2019 19:49:30 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 25A106B000C; Fri, 4 Oct 2019 19:49:30 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0079.hostedemail.com [216.40.44.79]) by kanga.kvack.org (Postfix) with ESMTP id 02ABC6B0008 for ; Fri, 4 Oct 2019 19:49:29 -0400 (EDT) Received: from smtpin03.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with SMTP id 9CC8D824376A for ; Fri, 4 Oct 2019 23:49:29 +0000 (UTC) X-FDA: 76007746458.03.frogs19_8d07c0dac3707 X-HE-Tag: frogs19_8d07c0dac3707 X-Filterd-Recvd-Size: 2826 Received: from mga07.intel.com (mga07.intel.com [134.134.136.100]) by imf36.hostedemail.com (Postfix) with ESMTP for ; Fri, 4 Oct 2019 23:49:28 +0000 (UTC) X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by orsmga105.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 04 Oct 2019 16:49:27 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.67,258,1566889200"; d="scan'208";a="205963785" Received: from richard.sh.intel.com (HELO localhost) ([10.239.159.54]) by fmsmga001.fm.intel.com with ESMTP; 04 Oct 2019 16:49:25 -0700 Date: Sat, 5 Oct 2019 07:49:07 +0800 From: Wei Yang To: Rik van Riel Cc: Wei Yang , akpm@linux-foundation.org, kirill.shutemov@linux.intel.com, jglisse@redhat.com, mike.kravetz@oracle.com, khlebnikov@yandex-team.ru, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/rmap.c: reuse mergeable anon_vma as parent when fork Message-ID: <20191004234907.GC15415@richard> Reply-To: Wei Yang References: <20191004160632.30251-1-richardw.yang@linux.intel.com> <9358295b1d9cc173940a58038123128b4dafc5d0.camel@surriel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <9358295b1d9cc173940a58038123128b4dafc5d0.camel@surriel.com> User-Agent: Mutt/1.9.4 (2018-02-28) 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: On Fri, Oct 04, 2019 at 07:45:26PM -0400, Rik van Riel wrote: >On Sat, 2019-10-05 at 00:06 +0800, Wei Yang wrote: >> 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. >> >> Signed-off-by: Wei Yang > >Acked-by: Rik van Riel > Thanks >-- >All Rights Reversed. -- Wei Yang Help you, Help me