From patchwork Fri Oct 4 16:06:32 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Wei Yang X-Patchwork-Id: 11174973 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 8464B139A for ; Fri, 4 Oct 2019 16:06:59 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 58538222C0 for ; Fri, 4 Oct 2019 16:06:59 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 58538222C0 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 8E36C6B0007; Fri, 4 Oct 2019 12:06:58 -0400 (EDT) Delivered-To: linux-mm-outgoing@kvack.org Received: by kanga.kvack.org (Postfix, from userid 40) id 896096B0008; Fri, 4 Oct 2019 12:06:58 -0400 (EDT) X-Original-To: int-list-linux-mm@kvack.org X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7A9CC6B000A; Fri, 4 Oct 2019 12:06:58 -0400 (EDT) X-Original-To: linux-mm@kvack.org X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0009.hostedemail.com [216.40.44.9]) by kanga.kvack.org (Postfix) with ESMTP id 53B5D6B0007 for ; Fri, 4 Oct 2019 12:06:58 -0400 (EDT) Received: from smtpin08.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with SMTP id E051F1F1D for ; Fri, 4 Oct 2019 16:06:57 +0000 (UTC) X-FDA: 76006580874.08.art19_1f992412da126 X-Spam-Summary: 1,0,0,,d41d8cd98f00b204,richardw.yang@linux.intel.com,:akpm@linux-foundation.org:kirill.shutemov@linux.intel.com:jglisse@redhat.com:mike.kravetz@oracle.com:riel@surriel.com:khlebnikov@yandex-team.ru::linux-kernel@vger.kernel.org:richardw.yang@linux.intel.com,RULES_HIT:30054:30070:30090,0,RBL:192.55.52.43:@linux.intel.com:.lbl8.mailshell.net-62.18.0.100 64.95.201.95,CacheIP:none,Bayesian:0.5,0.5,0.5,Netcheck:none,DomainCache:0,MSF:not bulk,SPF:fn,MSBL:0,DNSBL:neutral,Custom_rules:0:0:0,LFtime:24,LUA_SUMMARY:none X-HE-Tag: art19_1f992412da126 X-Filterd-Recvd-Size: 3002 Received: from mga05.intel.com (mga05.intel.com [192.55.52.43]) by imf21.hostedemail.com (Postfix) with ESMTP for ; Fri, 4 Oct 2019 16:06:56 +0000 (UTC) X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga002.jf.intel.com ([10.7.209.21]) by fmsmga105.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 04 Oct 2019 09:06:55 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.67,256,1566889200"; d="scan'208";a="204360824" Received: from richard.sh.intel.com (HELO localhost) ([10.239.159.54]) by orsmga002.jf.intel.com with ESMTP; 04 Oct 2019 09:06:53 -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 Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Wei Yang Subject: [PATCH] mm/rmap.c: reuse mergeable anon_vma as parent when fork Date: Sat, 5 Oct 2019 00:06:32 +0800 Message-Id: <20191004160632.30251-1-richardw.yang@linux.intel.com> X-Mailer: git-send-email 2.17.1 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: 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: Konstantin Khlebnikov Acked-by: Rik van Riel --- mm/rmap.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/mm/rmap.c b/mm/rmap.c index d9a23bb773bf..12f6c3d7fd9d 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -262,6 +262,17 @@ 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; + 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 (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;