Date:   Thu,  2 Feb 2023 23:32:27 +0000
Mime-Version: 1.0
Message-ID: <20230202233229.3895713-1-yosryahmed@google.com>
Subject: [RFC PATCH v1 0/2] Ignore non-LRU-based reclaim in memcg reclaim
From:   Yosry Ahmed <yosryahmed@google.com>
To:     Alexander Viro <viro@zeniv.linux.org.uk>,
        "Darrick J. Wong" <djwong@kernel.org>,
        Christoph Lameter <cl@linux.com>,
        David Rientjes <rientjes@google.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        Roman Gushchin <roman.gushchin@linux.dev>,
        Hyeonggon Yoo <42.hyeyoo@gmail.com>,
        "Matthew Wilcox (Oracle)" <willy@infradead.org>,
        Miaohe Lin <linmiaohe@huawei.com>,
        David Hildenbrand <david@redhat.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Peter Xu <peterx@redhat.com>, NeilBrown <neilb@suse.de>,
        Shakeel Butt <shakeelb@google.com>,
        Michal Hocko <mhocko@kernel.org>
Cc:     linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-xfs@vger.kernel.org, linux-mm@kvack.org,
        Yosry Ahmed <yosryahmed@google.com>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

Reclaimed pages through other means than LRU-based reclaim are tracked
through reclaim_state in struct scan_control, which is stashed in
current task_struct. These pages are added to the number of reclaimed
pages through LRUs. For memcg reclaim, these pages generally cannot be
linked to the memcg under reclaim and can cause an overestimated count
of reclaimed pages. This short series tries to address that.

Patch 1 is just refactoring updating reclaim_state into a helper
function, and renames reclaimed_slab to just reclaimed, with a comment
describing its true purpose.

Patch 2 ignores pages reclaimed outside of LRU reclaim in memcg reclaim.

The original draft was a little bit different. It also kept track of
uncharged objcg pages, and reported them only in memcg reclaim and only
if the uncharged memcg is in the subtree of the memcg under reclaim.
This was an attempt to make reporting of memcg reclaim even more
accurate, but was dropped due to questionable complexity vs benefit
tradeoff. It can be revived if there is interest.

Yosry Ahmed (2):
  mm: vmscan: refactor updating reclaimed pages in reclaim_state
  mm: vmscan: ignore non-LRU-based reclaim in memcg reclaim

 fs/inode.c           |  3 +--
 fs/xfs/xfs_buf.c     |  3 +--
 include/linux/swap.h |  5 ++++-
 mm/slab.c            |  3 +--
 mm/slob.c            |  6 ++----
 mm/slub.c            |  5 ++---
 mm/vmscan.c          | 19 ++++++++++++++++---
 7 files changed, 27 insertions(+), 17 deletions(-)

-- 
2.39.1.519.gcb327c4b5f-goog