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=-8.3 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,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 DBBA5C4360C for ; Fri, 4 Oct 2019 16:33:59 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 594D9222BE for ; Fri, 4 Oct 2019 16:33:59 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=yandex-team.ru header.i=@yandex-team.ru header.b="T6SmeEEZ" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 594D9222BE Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=yandex-team.ru Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id F395F6B0003; Fri, 4 Oct 2019 12:33:58 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id EE9E26B0005; Fri, 4 Oct 2019 12:33:58 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id DD7366B000A; Fri, 4 Oct 2019 12:33:58 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0075.hostedemail.com [216.40.44.75]) by kanga.kvack.org (Postfix) with ESMTP id B6F1F6B0003 for ; Fri, 4 Oct 2019 12:33:58 -0400 (EDT) Received: from smtpin07.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with SMTP id 5E793824CA3D for ; Fri, 4 Oct 2019 16:33:58 +0000 (UTC) X-FDA: 76006648956.07.teeth34_79d6e3cd6a85d X-HE-Tag: teeth34_79d6e3cd6a85d X-Filterd-Recvd-Size: 4452 Received: from forwardcorp1o.mail.yandex.net (forwardcorp1o.mail.yandex.net [95.108.205.193]) by imf11.hostedemail.com (Postfix) with ESMTP for ; Fri, 4 Oct 2019 16:33:57 +0000 (UTC) Received: from mxbackcorp2j.mail.yandex.net (mxbackcorp2j.mail.yandex.net [IPv6:2a02:6b8:0:1619::119]) by forwardcorp1o.mail.yandex.net (Yandex) with ESMTP id 85C542E1569; Fri, 4 Oct 2019 19:33:54 +0300 (MSK) Received: from iva8-b53eb3f76dc7.qloud-c.yandex.net (iva8-b53eb3f76dc7.qloud-c.yandex.net [2a02:6b8:c0c:2ca1:0:640:b53e:b3f7]) by mxbackcorp2j.mail.yandex.net (nwsmtp/Yandex) with ESMTP id nWp6vumrBQ-XrN0IFUp; Fri, 04 Oct 2019 19:33:54 +0300 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yandex-team.ru; s=default; t=1570206834; bh=ukwWMT0M4WMAhyW+DY5+USKRuUhjpcCz/2GXBQpfOoE=; h=In-Reply-To:Message-ID:From:Date:References:To:Subject:Cc; b=T6SmeEEZp7N1X45t5VIybaCbKEBKRlCiNIj75gWi/hZJ9yt6CDzywcqjWB0ivHe4x pAvHEh7usqgYZ2+RrvAwlAS3aud304u+rKM1p3XNeqfFIuWrIfSxMVVHaMiUgf7mCp jlpg7l+eYLLIP7AQ6RWS4BkFX13/Vvnw1CXxZSBs= Authentication-Results: mxbackcorp2j.mail.yandex.net; dkim=pass header.i=@yandex-team.ru Received: from unknown (unknown [2a02:6b8:b080:8808::1:a]) by iva8-b53eb3f76dc7.qloud-c.yandex.net (nwsmtp/Yandex) with ESMTPSA id PRCoHVn9Jm-XrH877W3; Fri, 04 Oct 2019 19:33:53 +0300 (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client certificate not present) Subject: Re: [PATCH] mm/rmap.c: reuse mergeable anon_vma as parent when fork To: Wei Yang , akpm@linux-foundation.org, kirill.shutemov@linux.intel.com, jglisse@redhat.com, mike.kravetz@oracle.com, riel@surriel.com Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20191004160632.30251-1-richardw.yang@linux.intel.com> From: Konstantin Khlebnikov Message-ID: Date: Fri, 4 Oct 2019 19:33:53 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20191004160632.30251-1-richardw.yang@linux.intel.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-CA Content-Transfer-Encoding: 7bit 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 04/10/2019 19.06, 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. > Makes sense. This might have much bigger effect for scenarios when task unmaps holes in huge vma as red-zones between allocations and then forks. Acked-by: Konstantin Khlebnikov > Signed-off-by: Wei Yang > --- > 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; >