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 F0A903DEAC3; Tue, 9 Jun 2026 07:35:39 +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=1780990544; cv=none; b=t8RK0tA3M7bLqmVRL7VZ8iB99FBB9kytMBtG27LezKFoEzpN+VpNMlC+vlVHNg6IK6EbabN5nbjAkdbOrQ4PiPoych3YV1vtjyxgW2PD+E/Inw6Ro7XIxXYz4rTA9Holb97VnG05M2eOtPJZOLWndysbuocMoRsjy2kK3KY2M4s= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780990544; c=relaxed/simple; bh=KwUNQ9cZs/pIlSeDAu0pgxS8JGTfN/76PWxF0LhR1Jc=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=tHvJxC1NFeXnFABu8w2gYMJOzlfenOJRuxmjXwj9DDhUBZhbJs2+yNZmvdZJdMn6X1bBJSKZkww7ZnvIKHSzRbt0SlI2S1qCpIA1lmQ6061zKQdrAGBJvWTkf/pBEpb9zxU1GZD6Rh19SbKxMMUToY8LcrV9mYQfuH53i3LYY7I= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=QKM7zKoO; 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="QKM7zKoO" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 46D521F00893; Tue, 9 Jun 2026 07:35:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1780990539; bh=y7BX3CVcz1NCkcZ9VRBH6DdOLwzw/KIRmNNQBjRMkfQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=QKM7zKoOEGCmMOgjqz22FaKfmugoiB47u0nOGoRF+NOmN4l3nOkdpksy+GKxK4DWw 4WYMWzVXJI9bMUCaTElKkEpgWpCvycuMhBRMi9/Kyc7WnxI/o0F1HEYfT4OJPt2gwV riQ4+si0ZdaOzfmaT5XiUDCG1nF3cyT2H8LjMY2KxQcEhxAM6gjWI59jaAgMxBsZMd /J7YJBXZnPGAhxBqBCDJXfiw3gGo+Y6FCNaomGkb9Yt1KNyfICXjtq8UOOz61RIsXN SCVTcDdXsg9MUCvSC5qXuq6jKSFtShI3F19CxxVnfKCdj013Dw2LsQ4QuwouEHROp4 QJSRvJNsI0rbw== Date: Tue, 9 Jun 2026 08:35:29 +0100 From: Lorenzo Stoakes To: Lance Yang 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 Subject: Re: [PATCH v5 9/9] mm: switch deferred split shrinker to list_lru Message-ID: References: <20260609032058.23770-1-lance.yang@linux.dev> Precedence: bulk X-Mailing-List: cgroups@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260609032058.23770-1-lance.yang@linux.dev> 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? 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