From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 146C52E7384 for ; Thu, 28 May 2026 18:24:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779992666; cv=none; b=i2tpftdkuBxoeQEBNHpi3GI9ByHxAxwIVHPYQh9wrIVK+Km8jkcDD2iY/wBsJv0X7XdTfIQjYRCIsCRDKEfA5ACpU7cFX9S6291T7VuVK0QtspRan1zGCwoOqb9WpQSynjT8vO5pEXtVCfXuvdWn/+Rh7JSULewimKK/bT7vxpo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779992666; c=relaxed/simple; bh=mnEncgZNsOLoiBj56Gp1z/RGtURUjOQDS3VSxLaq3Ew=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=n+QcDUfpZQcNcAxi++aNW66JPVlTe36y6xcaz3VlG+FVzfgH+MOHTTf/pEtCxlzVucL7TkG7p4W6PtQlL2wbyZDx/QUaHd1WTIgFjjaNJEsDuctYnfhmt2rnVOHZ3FSnno6cCykspp3NAikEv/7YQdeBsZY6Ufd3qjftXwvqTJk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=f9vGQZ6P; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="f9vGQZ6P" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 990851F000E9; Thu, 28 May 2026 18:24:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1779992664; bh=gB4nu31yDCvzFZgkpHNlp8skj58NUE9KQQaYhdOVdhw=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=f9vGQZ6Pe9ocW5MvHzpFT+VZrU4hVYBEl4eVp14GRFda4FPq5o9xIWklJ/rrpVXFI 6//KYPeBd2BxM8zQtEqbEOlOD/7uyCU+CEOQpwD7IrjmzZaLnyD+S3Pd5Y95UGcfvj H09Qqv1Pw1xOvphodYgKrD0/jteonfbvID/pzIs5BTpjQQuitkEEoH0aZbs2mMs/Iy W9fsgtRAaDM8+EDyJ1wrc2hhP673KYLf70SelWLEBeZ1SSbt3ahk8YEJsZcOBtdnio j/1wsfbwbqYcqNo5jkQgVRukoLzwrFFiNg2/fGMGunnyviyRC7HG75XZO5uJiTn7Ws Wp+AuAF3Wl8IA== Message-ID: <0a805d5f-079a-4eaa-ae37-6b7355a96626@kernel.org> Date: Thu, 28 May 2026 20:24:20 +0200 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/compaction: respect cpusets when checking retry suitability Content-Language: en-US To: fujunjie , Andrew Morton , linux-mm@kvack.org, Zhongkun He Cc: Michal Hocko , Suren Baghdasaryan , Brendan Jackman , Johannes Weiner , Zi Yan , linux-kernel@vger.kernel.org References: From: "Vlastimil Babka (SUSE)" Autocrypt: addr=vbabka@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 5/26/26 14:22, fujunjie wrote: > should_compact_retry() handles COMPACT_SKIPPED by asking > compaction_zonelist_suitable() whether reclaim can make a later > compaction attempt worthwhile. That answer is used for the current > allocation, so it should follow the same zone eligibility rules as the > allocation itself. > > When cpusets are enabled, allocator slowpath decisions are marked with > ALLOC_CPUSET. The allocation path, direct compaction and reclaim retry > all skip zones rejected by __cpuset_zone_allowed(). > > compaction_zonelist_suitable() does not apply that filter. It only walks > ac->zonelist/ac->nodemask, so it can return true because a zone that is > not usable for the current allocation would pass __compaction_suitable(). > > That does not let the allocation use the disallowed zone. Later > allocation and direct compaction paths still apply cpuset filtering. > However, it can make should_compact_retry() retry based on memory that > this allocation cannot use. > > Pass gfp_mask down and apply the same ALLOC_CPUSET check in > compaction_zonelist_suitable(). This keeps the retry decision aligned > with the zones that the allocation is allowed to use. Nice find. > A temporary debugfs probe was also used to call the old and new > compaction_zonelist_suitable() predicates in the same two-node NUMA guest. > The task was restricted to mems=0 while ac->nodemask covered nodes 0-1. > After putting pressure on node0, node0 failed __compaction_suitable() for > order-10 and node1 passed it, but node1 was rejected by > __cpuset_zone_allowed(). In that state the old predicate returned true and > the patched predicate returned false. Nice that you verified it like this. > Signed-off-by: fujunjie Reviewed-by: Vlastimil Babka (SUSE) Also probably this? That commit introduced the other cpuset checks for direct compaction. Fixes: 435b3894e742 ("mm:page_alloc: fix the NULL ac->nodemask in __alloc_pages_slowpath()") (not stable material though) Thanks! > --- > include/linux/compaction.h | 2 +- > mm/compaction.c | 6 +++++- > mm/page_alloc.c | 15 +++++++++------ > 3 files changed, 15 insertions(+), 8 deletions(-) > > diff --git a/include/linux/compaction.h b/include/linux/compaction.h > index 173d9c07a895..c829c48d1c71 100644 > --- a/include/linux/compaction.h > +++ b/include/linux/compaction.h > @@ -101,7 +101,7 @@ extern void compaction_defer_reset(struct zone *zone, int order, > bool alloc_success); > > bool compaction_zonelist_suitable(struct alloc_context *ac, int order, > - int alloc_flags); > + int alloc_flags, gfp_t gfp_mask); > > extern void __meminit kcompactd_run(int nid); > extern void __meminit kcompactd_stop(int nid); > diff --git a/mm/compaction.c b/mm/compaction.c > index 3648ce22c807..2295b2487dfc 100644 > --- a/mm/compaction.c > +++ b/mm/compaction.c > @@ -2447,7 +2447,7 @@ bool compaction_suitable(struct zone *zone, int order, unsigned long watermark, > > /* Used by direct reclaimers */ > bool compaction_zonelist_suitable(struct alloc_context *ac, int order, > - int alloc_flags) > + int alloc_flags, gfp_t gfp_mask) > { > struct zone *zone; > struct zoneref *z; > @@ -2460,6 +2460,10 @@ bool compaction_zonelist_suitable(struct alloc_context *ac, int order, > ac->highest_zoneidx, ac->nodemask) { > unsigned long available; > > + if (cpusets_enabled() && (alloc_flags & ALLOC_CPUSET) && > + !__cpuset_zone_allowed(zone, gfp_mask)) > + continue; > + > /* > * Do not consider all the reclaimable memory because we do not > * want to trash just for a single high order allocation which > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index ddeb79fa12db..93d56ba339fb 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -4199,7 +4199,8 @@ __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order, > } > > static inline bool > -should_compact_retry(struct alloc_context *ac, int order, int alloc_flags, > +should_compact_retry(gfp_t gfp_mask, struct alloc_context *ac, int order, > + int alloc_flags, > enum compact_result compact_result, > enum compact_priority *compact_priority, > int *compaction_retries) > @@ -4221,7 +4222,8 @@ should_compact_retry(struct alloc_context *ac, int order, int alloc_flags, > * migration targets. Continue if reclaim can help. > */ > if (compact_result == COMPACT_SKIPPED) { > - ret = compaction_zonelist_suitable(ac, order, alloc_flags); > + ret = compaction_zonelist_suitable(ac, order, alloc_flags, > + gfp_mask); > goto out; > } > > @@ -4274,7 +4276,8 @@ __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order, > } > > static inline bool > -should_compact_retry(struct alloc_context *ac, int order, int alloc_flags, > +should_compact_retry(gfp_t gfp_mask, struct alloc_context *ac, int order, > + int alloc_flags, > enum compact_result compact_result, > enum compact_priority *compact_priority, > int *compaction_retries) > @@ -4892,9 +4895,9 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order, > * of free memory (see __compaction_suitable) > */ > if (did_some_progress > 0 && can_compact && > - should_compact_retry(ac, order, alloc_flags, > - compact_result, &compact_priority, > - &compaction_retries)) > + should_compact_retry(gfp_mask, ac, order, alloc_flags, > + compact_result, &compact_priority, > + &compaction_retries)) > goto retry; > > /* Reclaim/compaction failed to prevent the fallback */ > > base-commit: e8c2f9fdadee7cbc75134dc463c1e0d856d6e5c7