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 A4701C46CD2 for ; Tue, 30 Jan 2024 09:35:50 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 371586B0078; Tue, 30 Jan 2024 04:35:50 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 2F9BE6B00A3; Tue, 30 Jan 2024 04:35:50 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 127E06B00A4; Tue, 30 Jan 2024 04:35:50 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id ED0986B00A3 for ; Tue, 30 Jan 2024 04:35:49 -0500 (EST) Received: from smtpin25.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id B46E81C1030 for ; Tue, 30 Jan 2024 09:35:49 +0000 (UTC) X-FDA: 81735470418.25.5324ABD Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.223.130]) by imf22.hostedemail.com (Postfix) with ESMTP id 65103C0014 for ; Tue, 30 Jan 2024 09:35:47 +0000 (UTC) Authentication-Results: imf22.hostedemail.com; dkim=pass header.d=suse.com header.s=susede1 header.b=fCMZrZ2D; dkim=pass header.d=suse.com header.s=susede1 header.b=fCMZrZ2D; dmarc=pass (policy=quarantine) header.from=suse.com; spf=pass (imf22.hostedemail.com: domain of mhocko@suse.com designates 195.135.223.130 as permitted sender) smtp.mailfrom=mhocko@suse.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1706607347; a=rsa-sha256; cv=none; b=3RRlkkW2bSVtEjdApd/0HuHyDexH4QlDMUYYZLkVIN1a4eRnZYLy5mB801QWzVyVBZ7oa8 6AGckRkyZpvzLlkCXjn9ZEuoOwZ772JQj8P2JrxlhfyOGqzqvo46AnBOKn/wEdeis9nUfM Es2bfQaOpFsSmahPHDc0V2AJk9Iqr/Y= ARC-Authentication-Results: i=1; imf22.hostedemail.com; dkim=pass header.d=suse.com header.s=susede1 header.b=fCMZrZ2D; dkim=pass header.d=suse.com header.s=susede1 header.b=fCMZrZ2D; dmarc=pass (policy=quarantine) header.from=suse.com; spf=pass (imf22.hostedemail.com: domain of mhocko@suse.com designates 195.135.223.130 as permitted sender) smtp.mailfrom=mhocko@suse.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1706607347; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=PHkeiCNSJCal3HVcuXxyv9aH6tYkcVNIKrc28/mzGBo=; b=5B9SHOkdYSQ7SMWJ1DyVmY+kHahoLw/F5XFYfsdAgGfmGCr/l6319T+5WqhlDKFV7JPPjI QvOPjcaKZYVW2CP+eE29YnoVCOvbcTRojleyTfsSujUkwNMoH9nUmI6odA9Pr0fU+wnQJI /mFlZBfiqzXEGMSGrh/p8/wvpsCYfZo= Received: from imap1.dmz-prg2.suse.org (imap1.dmz-prg2.suse.org [10.150.64.97]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id A0CB221DF4; Tue, 30 Jan 2024 09:35:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1706607345; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=PHkeiCNSJCal3HVcuXxyv9aH6tYkcVNIKrc28/mzGBo=; b=fCMZrZ2DVjQXelsv6h/YB/zS3aF3KiW7Pzr5RQqS4xBmenCplxkOIS9gYvrpqVxIqIPm2y dAVdfqLKRFHNjhFWMW5d+LibMsUmtO0pabX0RfLHeAQWJjyBIFnwC5t0C6Q3Zh1glDLswm khKMGgZufmuuqZQGjkrt6eud1p402NU= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1706607345; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=PHkeiCNSJCal3HVcuXxyv9aH6tYkcVNIKrc28/mzGBo=; b=fCMZrZ2DVjQXelsv6h/YB/zS3aF3KiW7Pzr5RQqS4xBmenCplxkOIS9gYvrpqVxIqIPm2y dAVdfqLKRFHNjhFWMW5d+LibMsUmtO0pabX0RfLHeAQWJjyBIFnwC5t0C6Q3Zh1glDLswm khKMGgZufmuuqZQGjkrt6eud1p402NU= Received: from imap1.dmz-prg2.suse.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by imap1.dmz-prg2.suse.org (Postfix) with ESMTPS id 7602913A6A; Tue, 30 Jan 2024 09:35:45 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id MxG9GfHCuGXlIwAAD6G6ig (envelope-from ); Tue, 30 Jan 2024 09:35:45 +0000 Date: Tue, 30 Jan 2024 10:35:40 +0100 From: Michal Hocko To: Lance Yang Cc: akpm@linux-foundation.org, zokeefe@google.com, david@redhat.com, songmuchun@bytedance.com, shy828301@gmail.com, peterx@redhat.com, minchan@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/1] mm/khugepaged: bypassing unnecessary scans with MMF_DISABLE_THP check Message-ID: References: <20240129054551.57728-1-ioworker0@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 65103C0014 X-Stat-Signature: okhtffafcygi963ohxmntetr5nqhau6j X-HE-Tag: 1706607347-360481 X-HE-Meta: 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 ubYhru0C Qd+00IOJqcp0VKISxVIukkERYGAXp05JLdwNkUelSRe8UA/Qh6cvDa8h9a7tivvE3zZK9n+s1xZHmxCxb55QIRQZuZAhgN8CXkVgXaTgYn2Z5sBCiZSjoDOw4jfVRz1amFqSjL4qQsYqBVA0mDng7yIGwUjLbkaU9SmLX2EEWMCVyv3iOT8YFXZKwyznEBh1Vlpd4Q6w4aRgXFmjstsqwvuU4u49tXHszUi0Txa3Fd50F5xLx0q3/VebNqlENNlQK6P3UQD/2kDvFZ6sjbo5HjfsvGwah25hfJ7/LGMOrkwb6tf68xq1h9rJCtA== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000015, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue 30-01-24 11:08:10, Lance Yang wrote: > On Tue, Jan 30, 2024 at 10:12 AM Lance Yang wrote: > > > > Hey Michal, > > > > Thanks for taking time to review! > > > > On some servers within our company, we deploy a > > daemon responsible for monitoring and updating > > local applications. Some applications prefer not to > > use THP, so the daemon calls prctl to disable THP > > before fork/exec. Conversely, for other applications, > > the daemon calls prctl to enable THP before fork/exec. > > > > Ideally, the daemon should invoke prctl after the fork, > > but its current implementation follows the described > > approach. > > In the Go standard library, there is no direct encapsulation > of the fork system call. Instead, fork and execve are > combined into one through syscall.ForkExec. OK, this is an important detail. Something that should be a part of the chnagelog. It is also important to note that this is not a correctness issue but rather an optimization to save expensive checks on each VMA when userspace cannot prctl itself before spawning into the new process. -- Michal Hocko SUSE Labs