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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7F8AFC433EF for ; Wed, 1 Jun 2022 05:20:46 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 0669C6B0074; Wed, 1 Jun 2022 01:20:46 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 0162F6B0075; Wed, 1 Jun 2022 01:20:45 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E1EA66B0078; Wed, 1 Jun 2022 01:20:45 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id D33676B0074 for ; Wed, 1 Jun 2022 01:20:45 -0400 (EDT) Received: from smtpin04.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id 913B934F93 for ; Wed, 1 Jun 2022 05:20:45 +0000 (UTC) X-FDA: 79528517250.04.860227D Received: from mail-pl1-f182.google.com (mail-pl1-f182.google.com [209.85.214.182]) by imf03.hostedemail.com (Postfix) with ESMTP id 504592004C for ; Wed, 1 Jun 2022 05:20:26 +0000 (UTC) Received: by mail-pl1-f182.google.com with SMTP id c2so760864plh.2 for ; Tue, 31 May 2022 22:20:39 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance-com.20210112.gappssmtp.com; s=20210112; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=8Zs32ZPOynrEtHOmKf2nU4IhPW8qkjU7KLDsMZ2L2Ew=; b=twDGCdvFNk9jkCYmzOBb1DVlWctmg/B+8+Txv/QglxY9J+O93oyrVJtilTCvm/fZUy vxUbo7u1yKiy+Ae49ge9H3zjUnEye+wN1C2IfM1HrZYFhMsyVHgrfi6ZCDpRwaa+eBya CiPKd0aQkjizhIu3MzppaCCXFW3Q6oCC/BnyzNWn4w10aIRzQLemPa3UjNxV4kRNlyd0 nFZ6cyJoViNDjf4NjOXJ3/sEuoUDgE2t1Loc7/MWBfU11WRqs+x8WZf5PBhXu/kMy/A8 gRJXcLbgUdo3ZimnjrITqJ3xtXgJjtXdNG5eSZDDypWBqPXUzduIT/sQrnlIgeUD1meM pQEg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=8Zs32ZPOynrEtHOmKf2nU4IhPW8qkjU7KLDsMZ2L2Ew=; b=Tg/vF70yJuNtPgllcndKQOeBeSH9Dz+W0OTYSuGb+Jsd9hgy7jJK+nNboVJPT+bJYV VA13efkubO8neLcyY9KVsxkyyVKkD13SlaeoQAhea3VfeG6gBRyVmh7tF4ZsyiNRjZ5S PHExNkuygfh7f1f4bUI4COEoKbe5BwpESMFT3xW4YJhgG9yUO6MmtvwGEGritZ3Qn6Eu rD8C5Z7djINldeiQy9e8QoFLhxNlkhOBPs44cw/9PWhyPwIdJ/I6EVaq/JgHKNFBgQmY 2vZw0VJWR6mOZQWVvgI/KvV2DsS9AcY4WwQ3h1M+Fuv5PlWb8g8+npWbieZQ8M78yjah enlg== X-Gm-Message-State: AOAM531R87SIAi33U90mU3/fi1fNH7nIb4xAk7RSPThxstqrn1zPwCe/ krtp66k4ROAW8c3HuSBjuJyk3w== X-Google-Smtp-Source: ABdhPJw8u9k5GyAD5lEhgf42ZHRNtsyafUtU/fTyVQQ7UxXZgbH9ecYW/TIRlnOzmVQURtXdF0jZbA== X-Received: by 2002:a17:902:ce87:b0:163:fc5e:398b with SMTP id f7-20020a170902ce8700b00163fc5e398bmr8413696plg.125.1654060838531; Tue, 31 May 2022 22:20:38 -0700 (PDT) Received: from localhost ([2408:8207:18da:2310:55b0:2d1a:e847:9fba]) by smtp.gmail.com with ESMTPSA id v11-20020a62a50b000000b0051ba97b788bsm404566pfm.27.2022.05.31.22.20.36 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 31 May 2022 22:20:38 -0700 (PDT) Date: Wed, 1 Jun 2022 13:20:30 +0800 From: Muchun Song To: Mike Kravetz Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Michal Hocko , Peter Xu , Naoya Horiguchi , James Houghton , Mina Almasry , "Aneesh Kumar K . V" , Anshuman Khandual , Paul Walmsley , Christian Borntraeger , Andrew Morton Subject: Re: [RFC PATCH 3/3] hugetlb: Lazy page table copies in fork() Message-ID: References: <20220527225849.284839-1-mike.kravetz@oracle.com> <20220527225849.284839-4-mike.kravetz@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220527225849.284839-4-mike.kravetz@oracle.com> Authentication-Results: imf03.hostedemail.com; dkim=pass header.d=bytedance-com.20210112.gappssmtp.com header.s=20210112 header.b=twDGCdvF; dmarc=pass (policy=none) header.from=bytedance.com; spf=pass (imf03.hostedemail.com: domain of songmuchun@bytedance.com designates 209.85.214.182 as permitted sender) smtp.mailfrom=songmuchun@bytedance.com X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 504592004C X-Rspam-User: X-Stat-Signature: p4a6n7mzzfuwhnk8uenmxrhico54wbjp X-HE-Tag: 1654060826-663644 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, May 27, 2022 at 03:58:49PM -0700, Mike Kravetz wrote: > Lazy page table copying at fork time was introduced with commit > d992895ba2b2 ("Lazy page table copies in fork()"). At the time, > hugetlb was very new and did not support page faulting. As a result, > it was excluded. When full page fault support was added for hugetlb, > the exclusion was not removed. > > Simply remove the check that prevents lazy copying of hugetlb page > tables at fork. Of course, like other mappings this only applies to > shared mappings. > > Lazy page table copying at fork will be less advantageous for hugetlb > mappings because: > - There are fewer page table entries with hugetlb > - hugetlb pmds can be shared instead of copied > > In any case, completely eliminating the copy at fork time shold speed > things up. > > Signed-off-by: Mike Kravetz Acked-by: Muchun Song Thanks.