Re: [PATCH v1 0/2] Ignore non-LRU-based reclaim in memcg reclaim

Yosry Ahmed
2023-03-08T06:55:32Z

On Tue, Feb 28, 2023 at 12:50 AM Yosry Ahmed <yosryahmed@google.com> wrote:
>
> 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 pages are uncharged anyway, so even if we end up under-reporting
> reclaimed pages we will still succeed in making progress during
> charging.
>
> Do not let the diff stat trick you, patch 2 is a one-line change. All
> the rest is moving a couple of functions around and a huge comment :)
>
> RFC -> v1:
> - Exported report_freed_pages in case XFS is built as a module (Matthew
> Wilcox).
> - Renamed reclaimed_slab to reclaim in previously missed MGLRU code.
> - Refactored using reclaim_state to update sc->nr_reclaimed into a
> helper and added an XL comment explaining why we ignore
> reclaim_state->reclaimed in memcg reclaim (Johannes Weiner).
>
> 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 | 79 +++++++++++++++++++++++++++++++++++---------
> 7 files changed, 74 insertions(+), 30 deletions(-)
>
> --
> 2.39.2.722.g9855ee24e9-goog
>

Friendly ping on this series, any comments or thoughts -- especially
on the memcg side?