From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A33CF2C3268 for ; Wed, 3 Dec 2025 11:28:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764761337; cv=none; b=oj5lqA/f3SIRSEcFq25bKUuszhn0uovRRXg/eAoZdjBHvqloSp2okHQXIHs/BNNf+Ga6TFwwjXfORpCIDSYl+/aWMMPjqRtSaLXNRUrEg8kXoSLyvbKnm0NVdzbR9/rejRuFMQxU1NLOuy77kCui3IHxIutHXlzF3X5Ay9L702A= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764761337; c=relaxed/simple; bh=WjtABvSbCCnx3nvKrk1EoRHpHn4A/68rGFxZqC4DWH8=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=HoV+9vOO9o0FAQyvT1EMag/tAsRQd9HdM6EisbLpHO0Bt8n30Vn0oolO0WAjA8EltQqvqOr4IcjqWB+28w7p1v/YB2rHiWT/gKSDKbucaDLjsK0Q6t1tocp0Cu4u8Aubl3kKL7lml0WzTOcxcjK1tI3PoaaBDMe8FGsBRx173NU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=JBl22uYM; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="JBl22uYM" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D5234C4CEFB; Wed, 3 Dec 2025 11:28:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1764761337; bh=WjtABvSbCCnx3nvKrk1EoRHpHn4A/68rGFxZqC4DWH8=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=JBl22uYMsIHsC6F3gqtDORz+MxQxHSbBOAiSBo1Xft5RQQbGgt3u7NN+kTir6Jhkk 1HUyrOhbg05uTTWQcxEE9EYbUue+bgPPA7mfmLCUMfZveif40kflHpRUgwM/wAosio PgG/kwk5iUi8Ar0sDBuqBJ9di/dfWfJOxk/cY1Tq50T0/qJGq5xNylDoT+oKxIV468 ddp8ZlwxT6EqgkI1/HqJne4XnVOT5QB/sfBSHj25srM3QTFHVaG7EGbIVwyDUG0yIq 1xfKegT6U4o7SfaivnusJbg1MEk+T4PiTJ+apuAO/l9r9+yPH1+IIpvhaZ3vHl/LcD M4mcRafKFJmeQ== Message-ID: <036614fd-e588-402c-8eb3-770ee9187bbd@kernel.org> Date: Wed, 3 Dec 2025 12:28:51 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/page_alloc: make percpu_pagelist_high_fraction reads lock-free To: Gregory Price Cc: Michal Hocko , Andrew Morton , Aboorva Devarajan , vbabka@suse.cz, surenb@google.com, jackmanb@google.com, hannes@cmpxchg.org, ziy@nvidia.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Oscar Salvador , Juan Yescas References: <20251201060009.1420792-1-aboorvad@linux.ibm.com> <20251201094112.07eb1e588b6da2ee70c4641d@linux-foundation.org> <47a8b4d5-f4d2-4772-b1b2-ee96bc21e742@kernel.org> <9de2f7e2-a202-499d-8858-6936beb251d9@kernel.org> From: "David Hildenbrand (Red Hat)" Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 12/3/25 10:23, Gregory Price wrote: > On Wed, Dec 03, 2025 at 10:08:55AM +0100, David Hildenbrand (Red Hat) wrote: >> On 12/3/25 10:02, Gregory Price wrote: >>> >>> My transient failure (although i'm not sure it was actually transient, i >>> killed it and retried after a few minutes and it succeeded immediately) >>> was on a ZONE_MOVABLE block. >> >> Okay, so that one should not bail out. Longterm pinnins must never end up on >> such memory, and if it happens, we have to identify why and fix it. >> >> We have this known problem of "stream of short-term pinnings" that can >> temporarily turn memory effectively unmovable. Juan will talk about that at >> LPC [1]. > > Nice, fun, good topic. Looking forward to Japan n_n > >> >> We have another set of problematic cases (vmsplice(), fuse) but I would >> assume that these are not the cases you are hitting. >> > > We do use fuse, but this system was relatively quiet when i tried this. > > We do have some proactive reclaim / demotion going on, but i don't think > it was that (see below). > >>> >>> Kind of suggested to me there was some bad condition the resolved once I >>> took a second to release the lock and try again. >> >> Hard to tell I'm afraid. Do you still have the dump_folio() calls we print >> when migration fails? >> > > What luck, I do! :D :) > And i just noticed it's the same page over and over > > [ 3404.119270] migrating pfn c06f176 failed ret:1 > [ 3404.129152] page: refcount:4 mapcount:0 mapping:0000000061ca20ba index:0xad28e5b pfn:0xc06f176 > [ 3404.148284] memcg:ffff88842e855000 > [ 3404.155834] aops:btree_aops ino:1 Small folio. Not GUP-pinned (FOLL_PIN, otherwise our refcount would be >= 1024. It could be ordinary GUP (FOLL_GET) e.g., from vmsplice or some older O_DIRECT user that was not converted to FOLL_PIN yet. But maybe it's just btrfs / something else that temporarily holds a folio reference. Given that this is from 6.13 ... hard to tell :) > [ 3404.163193] flags: 0x17ffff066c00420c(referenced|uptodate|workingset|private|node=1|zone=3|lastcpupid=0x1ffff) Neither dirty nor under writeback. -- Cheers David