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]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 30F0EC531FA for ; Fri, 24 Jul 2026 15:01:05 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 1096B6B008A; Fri, 24 Jul 2026 11:01:04 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 0BB2A6B008C; Fri, 24 Jul 2026 11:01:04 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id EC3C36B0092; Fri, 24 Jul 2026 11:01:03 -0400 (EDT) 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 B7E766B008A for ; Fri, 24 Jul 2026 11:01:03 -0400 (EDT) Received: from smtpin24.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay08.hostedemail.com (Postfix) with ESMTP id 213901403A0 for ; Fri, 24 Jul 2026 15:01:03 +0000 (UTC) X-FDA: 85023982806.24.6C13206 Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf16.hostedemail.com (Postfix) with ESMTP id 58A05180008 for ; Fri, 24 Jul 2026 15:01:01 +0000 (UTC) Authentication-Results: imf16.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=e8W6X5M2; spf=pass (imf16.hostedemail.com: domain of vbabka@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=vbabka@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1784905261; 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=kuWKgYJKiGV4VnZawJ+31C9x8fGlUZAxGdZ/7YC2SfQ=; b=7QcbR/ngkr4YeDEV6amxHvzoKTSTbGyR/8vMbC/W1fv7VBah0HLpuJQF7ORCuG7SZHzSwv XC9iadw74fK7CSu29V8zwATxHTHpqI3eXbmxx2kYGQmbqRgJlGVXkAThQ9KzpDE8lwE2uX QUMtR35+WTUvhV+qG6EWMCfYMNkMK0I= ARC-Authentication-Results: i=1; imf16.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=e8W6X5M2; spf=pass (imf16.hostedemail.com: domain of vbabka@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=vbabka@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1784905261; b=MBokgBc6bWiMn6SN54wu8FI6kSl1pFq6B7Jb6bolHIolrXUwF2raF5NebKS1SO8o/vsuNJ QCJJ9GVLC/WI8wi683fmHroh59WbHhYQj90voOcNFgFalcesxeankW12OuHIXvicEQGbJJ CE6U+nUvzXkUQcBRDBL+Wn8Kd6vftt0= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id 65F33600B0; Fri, 24 Jul 2026 15:01:00 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 874C11F000E9; Fri, 24 Jul 2026 15:00:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1784905260; bh=kuWKgYJKiGV4VnZawJ+31C9x8fGlUZAxGdZ/7YC2SfQ=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=e8W6X5M2pWsGtZi5XaJpnWsvWT++ncbBXhDqFjs8KD0up2kycu/GMZbclBqiYBpSt wGzBMfmT23dSVR2aOyK3651NPXs6EiED71CrPgklCvktIgQIhU01/x2l2RJV32mRUb I61yvMTDXNEj8/Qnqjv/d5VsR3GZRx5THPnfMJJJST27AmgHSZXc+e0Y0wb7c+q2i1 0QmyTiTnRi3iUuGrsUSWf21jiNgRfMYLqSo8x/i9HorgD9ELZuNaXx51c0diW3/Yv5 znuxqK3yOKhTHRPlenaKzAkp2IxQCW6Xev/WewcVy0CG5AMyMXyRrCxf3PLIVE2EO7 ms5vOavVoI+lQ== Message-ID: <7b403326-b716-4766-9488-3bf662b74a64@kernel.org> Date: Fri, 24 Jul 2026 17:00:56 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/mlock: skip __mm_populate() for MLOCK_ONFAULT Content-Language: en-US To: "Lorenzo Stoakes (ARM)" , Wandun Chen Cc: liam@infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, jannh@google.com, pfalcato@suse.de References: <20260722125133.543441-1-chenwandun1@gmail.com> From: "Vlastimil Babka (SUSE)" Autocrypt: addr=vbabka@kernel.org; keydata= xsFNBFZdmxYBEADsw/SiUSjB0dM+vSh95UkgcHjzEVBlby/Fg+g42O7LAEkCYXi/vvq31JTB KxRWDHX0R2tgpFDXHnzZcQywawu8eSq0LxzxFNYMvtB7sV1pxYwej2qx9B75qW2plBs+7+YB 87tMFA+u+L4Z5xAzIimfLD5EKC56kJ1CsXlM8S/LHcmdD9Ctkn3trYDNnat0eoAcfPIP2OZ+ 9oe9IF/R28zmh0ifLXyJQQz5ofdj4bPf8ecEW0rhcqHfTD8k4yK0xxt3xW+6Exqp9n9bydiy tcSAw/TahjW6yrA+6JhSBv1v2tIm+itQc073zjSX8OFL51qQVzRFr7H2UQG33lw2QrvHRXqD Ot7ViKam7v0Ho9wEWiQOOZlHItOOXFphWb2yq3nzrKe45oWoSgkxKb97MVsQ+q2SYjJRBBH4 8qKhphADYxkIP6yut/eaj9ImvRUZZRi0DTc8xfnvHGTjKbJzC2xpFcY0DQbZzuwsIZ8OPJCc LM4S7mT25NE5kUTG/TKQCk922vRdGVMoLA7dIQrgXnRXtyT61sg8PG4wcfOnuWf8577aXP1x 6mzw3/jh3F+oSBHb/GcLC7mvWreJifUL2gEdssGfXhGWBo6zLS3qhgtwjay0Jl+kza1lo+Cv BB2T79D4WGdDuVa4eOrQ02TxqGN7G0Biz5ZLRSFzQSQwLn8fbwARAQABzSNWbGFzdGltaWwg QmFia2EgPHZiYWJrYUBrZXJuZWwub3JnPsLBsAQTAQoAWhYhBKlA1DSZLC6OmRA9UCJPp+fM gqZkBQJqFFy6GxSAAAAAAAQADm1hbnUyLDIuNSsxLjEyLDIsMgIbAwUJGtCBUAULCQgHAwUV CgkICwUWAgMBAAIeBQIXgAAKCRAiT6fnzIKmZJIUEADFx/tREzUImHrEwVHeSvDFmA7tJysI UVrlvrM09E7GIuzphzv7jYmo8n3ANpCczLEVr4G0syYQdTigaZgv3+FQDIIzhKih1IHhu1Ei XHlywNWKnQxxQEUNi5Mwx43wQz5XVw9F1A7gtKBKNtfogO511hAbrzagrYajyQacEJ/+sfhZ 9Da8ltHIXD8pcYaHUfQgEusCgmEd9+KrUwrTbckFKmYq5chuE6yJ4J0EmWknL096jIE6CnzF FRslQ3B1UKDjxVsm1ZHfir5NeWszLkTvGFsddFaWTgh8UycESG6VQzKXjjewXu2pG7YQYRpj QKm1W5X2TkwWkXRBZTmfmbhxIUMh3+zf5wQ463rSmDN/8v81tdqBtAW6rH/kzg1GvkaTHXn0 507yEHFzBksk2viAuIxxr7km8+/KARYLIdGtx30EG8cKzAUZOK6WqxtNCsXUJNrVE8CWrCaD icoNu7Fs1c5hmPHdSTnU48ce67449DdnO4neLSNhRiGlMHJgfJUmgrxu/hcYeOZ3haWmEQ2w uW1Mh01OHi8QZHCEyAbABrPs9GUgccc/4eYXX9hIgxfSkYzn8f+8NuIFPWl/0uTvjgqU29FQ SbzOLxHq9439Ox40G5mS5eZXRGxITYR+6TXvRGI6P/264jvflnr/pDGUttaikU+0W+1uxgKH cmYbEc7ATQRbGTU1AQgAn0H6UrFiWcovkh6EXVcl+SeqyO6JHOPm+e9Wu0Vw+VIUvXZVUVVQ La1PQDUi6j00ChlcR66g9/V0sPIcSutacPKfdKYOBvzd4rlhL8rfrdEsQw5ApZxrA8kYZVMh FmBRKAa6wos25moTlMKpCWzTH84+WO5+ziCTsTUZASAToz3RdunTD+vQcHj0GqNTPAHK63sf bAB2I0BslZkXkY1RLb/YhuA6E7JyEd2pilZOrIuBGl/5q2qSakgnAVFWFBR/DO27JuAksYnq +aH8vI0xGvwn75KqSk4UzAkDzWSmO4ZHuahKtQgZNsMYV+PGayRBX9b9zbldzopoLBdqHc4n jQARAQABwsF8BBgBCgAmAhsMFiEEqUDUNJksLo6ZED1QIk+n58yCpmQFAmfIHFQFCRYU6J8A CgkQIk+n58yCpmS2PA//bqN1LfcotmArgElsa+0EGZSQlYgK48pm8WAeTXTngudP9IJ4SuKY HR5RNjHcBeqN+Me0zxRqYzRb8nGanHEkDyf4Im8DQM8d6vbyU+FcPmG4skud4kgS1zMHnlVd SXfSIwKC/hKgdHG8aBV7545Lz9X6Iohea+94wneD0aw/hqF+QWewGZhWJriWAZtvEkzNjQOi 4U9F/trLten/x7bpphDSnDMKJtITbtzATT1Dq7o7VpIUK1nCTQALMuMjKCdi8OdU/+V+R3O4 0PXWvX8qrvqYapVbZ+9KqT74FsuB0Ya9uXwgBF2Q6cRuETZk5vqaqKxzqoQZCO8AOz/58j6O 2RHNy/mZEN+7tJ5Tsq42zVJ4jxsT8b9YplavCMsnBgDeRWhcbYhCyttoL7nYISyWg4kQYZ/P wIV3OuNv2f8iKYsxNsRuClOAF82+gvqOy1/1pprFjy8uo2pkoOrb63aOP3vO5VHnRKgra6dq NcaZ+c6J4H+nEJGi2SkHAUJz5oBzuThvPudLvPA/SK8sKoM01IRxSihev/S/5WLazXB1PGem OCbvzC1IjWJJraxiDJ5IygokapUa2RP7+WBR22skQ3SSl6G107QgWKSyTOGWEaRmV53vxQLV jXuCmzSSasTL60zq5yGrT4/DYQVSNEUiUbG4pYekxJujNeEDkUlky0Y= In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 58A05180008 X-Stat-Signature: uoueap4eua8gfgaksxjnuoyutfh95ooy X-HE-Tag: 1784905261-526075 X-HE-Meta: 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 izr58r6W QYpSZv4oDiODiZt/slMeAJ/xj0/4q1qQ5hd6xeeYiRJ7jCMyWtMPHJ4EEv8w1NL3UgoWLctdEMc5d5BOY+p1e1OmVZq0dlNuAB3YDaFcuewS5IpQp4paDc7KXf4l4b8EQlfWYPKnoMuIkjUCxLvTGsJV/gurgTakCZzTbYCFa+XhHsd3+CymiSJhzeA71/N/Jg6Yr1I9KWmczu9owb8uelK5VCgmAuimMB6+up2Xdp01n3j51M/n6qkspIJI2pBjjNZ1R5ebWiK8tF5wdbidbZH3bEtpK1rMKbN/khMmnIQfpRVpmFjkBVBh8Pxe8KzX4CO33Bss0uPCzukdI9dbSrnrbWSqVCUNMQ/KdrijcrED0O5A= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 7/22/26 14:59, Lorenzo Stoakes (ARM) wrote: > On Wed, Jul 22, 2026 at 08:51:33PM +0800, Wandun Chen wrote: >> From: Wandun Chen >> >> MLOCK_ONFAULT only locks pages on future faults, so there is no need to >> fault in non-present pages during the mlock2/mlockall syscall. >> populate_vma_page_range() already returns immediately for VMAs with >> VM_LOCKONFAULT, which means __mm_populate() just loops over VMAs and >> holds mmap_read_lock without doing useful work. >> >> Skip __mm_populate() when MLOCK_ONFAULT is set to avoid this unnecessary >> work. >> >> Signed-off-by: Wandun Chen > > Well you take mmap read lock and release it (after having held the write lock), > hardly earth-shattering. > > And this has been this way for donkey's years I don't really see why we should > care? > > Do you have a workload that's heavily dependent on mlock2(..., MLOCK_ONFAULT) or > mlockall(..., MCL_ONFAULT) as a hot path that is seriously contending the mmap > lock? > > I don't love how the VMA_LOCKONFAULT_BIT flag works but I'm not sure adding more > churn and code for the sake of it here is really worth it. > > Thanks, Lorenzo While that's true, I don't see a problem taking the patch. Otherwise we'll have to keep rejecting all future attempts (including LLM) doing the same because it just seems like a low hanging fruit to stop doing an unnecessary thing. And it's not that much of a churn or new code, IMHO. >> --- >> mm/mlock.c | 10 ++++++---- >> 1 file changed, 6 insertions(+), 4 deletions(-) >> >> diff --git a/mm/mlock.c b/mm/mlock.c >> index efa6716e4dfb..784bd4bfc3bb 100644 >> --- a/mm/mlock.c >> +++ b/mm/mlock.c >> @@ -658,9 +658,11 @@ static __must_check int do_mlock(unsigned long start, size_t len, >> if (error) >> return error; >> >> - error = __mm_populate(start, len, 0); >> - if (error) >> - return __mlock_posix_error_return(error); >> + if (!vma_flags_test(flags, VMA_LOCKONFAULT_BIT)) { >> + error = __mm_populate(start, len, 0); >> + if (error) >> + return __mlock_posix_error_return(error); >> + } >> return 0; >> } >> >> @@ -778,7 +780,7 @@ SYSCALL_DEFINE1(mlockall, int, flags) >> capable(CAP_IPC_LOCK)) >> ret = apply_mlockall_flags(flags); >> mmap_write_unlock(current->mm); >> - if (!ret && (flags & MCL_CURRENT)) >> + if (!ret && (flags & MCL_CURRENT) && !(flags & MCL_ONFAULT)) >> mm_populate(0, TASK_SIZE); >> >> return ret; >> -- >> 2.43.0 >>