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DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1780975283; 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=xlehNq+dGhjF8xlBwPq9xUEl93005P8DJEDN49foV2w=; b=FZke0vfO68yr6RGe+gmExYKpGubD3NRE4r0BoJb/bgJd1TBzspF/AJkmv3vdYQ21xphqqT GO3OdzWzK4UGast1YrK+Oz22+ee21ay+UTrsAJ/sfTXt82KPv26klQsKExZBVj2Y82Gykb gWOI/qBsQAz01ln6jRz1jxcjWYDh1vs= From: Lance Yang To: hannes@cmpxchg.org Cc: lance.yang@linux.dev, baolin.wang@linux.alibaba.com, akpm@linux-foundation.org, david@kernel.org, ljs@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 Date: Tue, 9 Jun 2026 11:20:58 +0800 Message-Id: <20260609032058.23770-1-lance.yang@linux.dev> In-Reply-To: References: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspamd-Queue-Id: 8DFD2140007 X-Stat-Signature: 3d4ab9cg1ekc3ptq9yfkhku8hfn861id X-Rspamd-Server: rspam03 X-Rspam-User: X-HE-Tag: 1780975287-391202 X-HE-Meta: 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 RnTXA4SA AQSfCk87ZjugJV0O2DMCDtMz4deHDTJ7qSLTev5FUrebIpLVp3MUwlKoy3EHYVYdlw4qlS8WTo79nJmB8VAWHY+uob+29Z46yKp+7jKQ0gZK6r+Z5WtxmAZEzFtoIuk94VNrgGYGT2nQs6yZ0MwuLv+rl+QrGHw4V5r1XvMjbdIvrBTt/Le0ulqpxp5JUtF62RSCI77PpE7Nsn2+nNNDhZjljLUrY/hkzUrfkjLVyI3Gj7hk/Y9T64XYjCXJB2422xqyylnZUNem/Lj5ixY1N0sri7A== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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) && + 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)