From: Ridong Chen <ridong.chen@linux.dev>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>,
David Hildenbrand <david@kernel.org>,
Michal Hocko <mhocko@kernel.org>, Qi Zheng <qi.zheng@linux.dev>,
Shakeel Butt <shakeel.butt@linux.dev>,
Lorenzo Stoakes <ljs@kernel.org>,
Kairui Song <kasong@tencent.com>, Barry Song <baohua@kernel.org>,
Axel Rasmussen <axelrasmussen@google.com>,
Yuanchu Xie <yuanchu@google.com>, Wei Xu <weixugc@google.com>,
Zhongkun He <hezhongkun.hzk@bytedance.com>,
Muchun Song <muchun.song@linux.dev>,
Davidlohr Bueso <dave@stgolabs.net>,
Roman Gushchin <roman.gushchin@linux.dev>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Ridong Chen <chenridong@xiaomi.com>
Subject: Re: [PATCH v3 0/4] mm/vmscan: fix swappiness=max and clean up per-node proactive reclaim
Date: Fri, 24 Jul 2026 10:43:22 +0800 [thread overview]
Message-ID: <8336e48a-ab3a-4db9-a7f9-5bb6af2b22c3@linux.dev> (raw)
In-Reply-To: <20260723171842.137e45eb36b21b3b45245da0@linux-foundation.org>
On 7/24/2026 8:18 AM, Andrew Morton wrote:
> On Thu, 23 Jul 2026 12:57:14 +0800 Ridong <ridong.chen@linux.dev> wrote:
>
>> Fixes and one cleanup.
>>
>> Patch 1 fixes "swappiness=max": the anon-only test in get_scan_count()
>> sat after the "cannot reclaim anon" check, so when no anon was
>> reclaimable the request fell back to SCAN_FILE and evicted page cache
>> instead.
>>
>> Patch 2 fixes reclaim_store() collapsing every error into -EAGAIN, so
>> callers can no longer tell an invalid argument from a busy interface;
>> propagate the real error code, matching the memcg path.
>>
>> Patch 3 drops the now-unused gfp_mask parameter from __node_reclaim().
>>
>> Patch 4 fixes the same "swappiness=max" issue for MGLRU.
>
> Thanks. AI review might have found several pre-existing issues which
> might interest the maintainers. Also a suggestion against your [4/4]:
>
> https://sashiko.dev/#/patchset/20260723045718.2052070-1-ridong.chen@linux.dev
Hi all, sashiko review:
This is a pre-existing issue, but I noticed that per-node proactive reclaim
fails to reclaim memory if the node's unmapped file or slab pages are below
minimum thresholds, completely ignoring anonymous memory.
In mm/vmscan.c:__node_reclaim():
if (node_pagecache_reclaimable(pgdat) > pgdat->min_unmapped_pages ||
node_page_state_pages(pgdat, NR_SLAB_RECLAIMABLE_B) >
pgdat->min_slab_pages) {
Does this condition incorrectly block proactive reclaim of anonymous memory
by applying legacy zone-reclaim thresholds?
It seems to bypass shrink_node() entirely if file/slab pages are low, even
when sc->proactive is set, which could falsely return -EAGAIN to userspace
for anon-heavy workloads.
Should we add:
if (sc->proactive ||
node_pagecache_reclaimable(pgdat) > pgdat->min_unmapped_pages ||
node_page_state_pages(pgdat, NR_SLAB_RECLAIMABLE_B) > pgdat->min_slab_pages) {
--
Best regards
Ridong
prev parent reply other threads:[~2026-07-24 2:43 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-23 4:57 [PATCH v3 0/4] mm/vmscan: fix swappiness=max and clean up per-node proactive reclaim Ridong
2026-07-23 4:57 ` [PATCH v3 1/4] mm/vmscan: fix anon-only reclaim evicting file pages when swappiness=max Ridong
2026-07-23 4:57 ` [PATCH v3 2/4] mm: vmscan: propagate real error code from per-node proactive reclaim Ridong
2026-07-23 4:57 ` [PATCH v3 3/4] mm: vmscan: drop unused gfp_mask parameter from __node_reclaim() Ridong
2026-07-23 4:57 ` [PATCH v3 4/4] mm/mglru: fix anon-only reclaim evicting file pages when swappiness=max Ridong
2026-07-23 8:57 ` Barry Song
2026-07-24 2:20 ` Ridong Chen
2026-07-24 0:18 ` [PATCH v3 0/4] mm/vmscan: fix swappiness=max and clean up per-node proactive reclaim Andrew Morton
2026-07-24 2:27 ` Ridong Chen
2026-07-24 2:43 ` Ridong Chen [this message]
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