From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-184.mta0.migadu.com (out-184.mta0.migadu.com [91.218.175.184]) (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 2C5E13E1208 for ; Tue, 9 Jun 2026 08:03:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.184 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780992189; cv=none; b=jpDxbGN1U4EPG4uMgjSf9UIiW7Am+CyuEmCZyZuz+9DWcvO2nmqwTrBsBXyvE58NAca6UESRzi4ELl0EGzsKyD/USyNYh3lrojfbxoydyCo868VJHZk9m46Fgh7Mf9I6Ton6ypUVvwH8ELWnnyb/LRo6/F5yGA+eXg3u02f+B3U= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780992189; c=relaxed/simple; bh=7psJ3mXqxC7gENVmGvzWQwN73nK6rdrC51N5aD5Igec=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=ImQ6RCQYX2DE6gwGbhGsVOC+Z/MDj1JZy6QkpRXiyS65Hy1M33Wrvq7JVUCsvFhWA8qRFslpbd90qfK4nom83btw5jzJU+zPv72aRbtYeCLa46vYuWwWKVmD9FDcwaUbqE9sXws3ew9OoKty3Po+ET421DoR9lHwneTmmRbkOuY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=jRsT/4aB; arc=none smtp.client-ip=91.218.175.184 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="jRsT/4aB" Message-ID: <3306b3b4-a063-43f9-a740-2311dd87be3c@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1780992180; h=from:from: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; bh=AUcVuWAo1N6d6dSjCQRntUYShy5LQAwX8omMTfd5mYY=; b=jRsT/4aBlYtkb7QyMASuQsaRCIGhVQN28SEQahPXRkP6GdrPmLYHyV3FPEJEvccUtoUjgS bqwbEEfE3urBD6PIGshjjfBeQMLGqIgDhPHFvxB1Pdzq/taY9MywfQfbiAgh8BaO4tcAgd CgI1a9LIBP+8p3ujctXEZz1NlV8s3XI= Date: Tue, 9 Jun 2026 16:02:46 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH v5 9/9] mm: switch deferred split shrinker to list_lru To: Lorenzo Stoakes Cc: hannes@cmpxchg.org, baolin.wang@linux.alibaba.com, akpm@linux-foundation.org, david@kernel.org, shakeel.butt@linux.dev, mhocko@kernel.org, david@fromorbit.com, roman.gushchin@linux.dev, muchun.song@linux.dev, qi.zheng@linux.dev, yosry.ahmed@linux.dev, ziy@nvidia.com, liam@infradead.org, usama.arif@linux.dev, kas@kernel.org, vbabka@kernel.org, ryncsn@gmail.com, zaslonko@linux.ibm.com, gor@linux.ibm.com, baohua@kernel.org, dev.jain@arm.com, npache@redhat.com, ryan.roberts@arm.com, cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20260609032058.23770-1-lance.yang@linux.dev> Content-Language: en-US X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Lance Yang In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT On 2026/6/9 15:35, Lorenzo Stoakes wrote: > On Tue, Jun 09, 2026 at 11:20:58AM +0800, Lance Yang wrote: >> >> On Mon, Jun 01, 2026 at 02:17:28PM -0400, Johannes Weiner wrote: >>> On Mon, Jun 01, 2026 at 09:21:35PM +0800, Lance Yang wrote: >>>> >>>> On Wed, May 27, 2026 at 04:45:16PM -0400, Johannes Weiner wrote: >>>> [...] >>>>> diff --git a/mm/swap_state.c b/mm/swap_state.c >>>>> index 04f5ce992401..9c3a5cf99778 100644 >>>>> --- a/mm/swap_state.c >>>>> +++ b/mm/swap_state.c >>>>> @@ -465,6 +465,16 @@ static struct folio *__swap_cache_alloc(struct swap_cluster_info *ci, >>>>> return ERR_PTR(-ENOMEM); >>>>> } >>>>> >>>> >>>> Shouldn't this be limited to anon swapin? >>>> >>>> e.g. vmf && vma_is_anonymous(vmf->vma) >>>> >>>>> + if (order > 1 && folio_memcg_alloc_deferred(folio)) { >>>> >>>> __swap_cache_alloc() is also used by shmem direct swapin, so shmem can >>>> get here too when handling a large swap entry: >>>> >>>> shmem_get_folio_gfp() >>>> shmem_swapin_folio() >>>> shmem_swap_alloc_folio() >>>> swapin_sync() >>>> swap_cache_alloc_folio() >>>> __swap_cache_alloc() >>>> folio_memcg_alloc_deferred() >>> >>> Good catch, I think you're right. I shouldn't have dismissed that >>> branch due to "/* Direct swapin skipping swap cache & readahead */" >>> >>>> @Baolin please correct me if I got it wrong :) >>>> >>>> folio_memcg_alloc_deferred() itself doesn't filter shmem out either; it >>>> only allocates the memcg list_lru metadata for deferred_split_lru: >>>> >>>> int folio_memcg_alloc_deferred(struct folio *folio) >>>> { >>>> if (mem_cgroup_disabled()) >>>> return 0; >>>> return folio_memcg_list_lru_alloc(folio, &deferred_split_lru, GFP_KERNEL); >>>> } >>>> >>>> Since deferred_split_lru only queues anon large folios, doing this for >>>> shmem swapin doesn't buy us anything :) >>> >>> Yes, agreed. I don't think it's a big deal / show stopper in terms of >>> user-visible effect, but of course still worth fixing. >>> >>> I'll send a follow-up patch. >> >> Thanks. >> >> Looks like this has already landed in mm-stable. If you're okay with it, >> I can send the follow-up. >> >> From: Lance Yang >> Date: Tue, 9 Jun 2026 10:56:45 +0800 >> Subject: [PATCH] mm: prepare deferred split metadata only for anon swapin >> >> __swap_cache_alloc() prepares deferred split metadata for large swapcache >> folios. >> >> That also covers shmem swapin, because shmem_swap_alloc_folio() can call >> swapin_sync() with a large order[1]. But shmem folios are not queued on >> the deferred split queue, so preparing the metadata doesn't buy us >> anything there. >> >> So let's limit it to anon swapin. >> >> [1] https://lore.kernel.org/all/20260601132135.14272-1-lance.yang@linux.dev/ >> >> Signed-off-by: Lance Yang >> --- >> mm/swap_state.c | 3 ++- >> 1 file changed, 2 insertions(+), 1 deletion(-) >> >> diff --git a/mm/swap_state.c b/mm/swap_state.c >> index 9c3a5cf99778..7adac957c2b8 100644 >> --- a/mm/swap_state.c >> +++ b/mm/swap_state.c >> @@ -465,7 +465,8 @@ static struct folio *__swap_cache_alloc(struct swap_cluster_info *ci, >> return ERR_PTR(-ENOMEM); >> } >> >> - if (order > 1 && folio_memcg_alloc_deferred(folio)) { >> + if (order > 1 && vma && vma_is_anonymous(vma) && > > A folio can be anon for a non-shmem file-backed VMA though? > E.g. MAP_PRIVATE-mapped file-backed mappings? Ah, good point! vma_is_anonymous() is too strong here ... Maybe use !vma_is_shmem(vma) instead? > Not sure if that's something that'd be a factor here/meaningful though. > >> + folio_memcg_alloc_deferred(folio)) { >> spin_lock(&ci->lock); >> __swap_cache_do_del_folio(ci, folio, entry, shadow); >> spin_unlock(&ci->lock); >> -- >> 2.39.3 (Apple Git-146) > > Cheers, Lorenzo