Re: [PATCH 0/5] btrfs: make extent map shrinker more efficient and re-enable it

[Josef Bacik <josef@toxicpanda.com>]

On Tue, Sep 24, 2024 at 11:45:40AM +0100, fdmanana@kernel.org wrote:
> From: Filipe Manana <fdmanana@suse.com>
> 
> This makes the extent map shrinker run by a single task and asynchronously
> in a work queue, re-enables it by default and some cleanups. More details
> in the changelogs of each patch.
> 
> Filipe Manana (5):
>   btrfs: add and use helper to remove extent map from its inode's tree
>   btrfs: make the extent map shrinker run asynchronously as a work queue job
>   btrfs: simplify tracking progress for the extent map shrinker
>   btrfs: rename extent map shrinker members from struct btrfs_fs_info
>   btrfs: re-enable the extent map shrinker
> 

I think as a first step this is good.

I am concerned that async shrinking under heavy memory pressure will
lead to spurious OOM's because we're never waiting for the async
shrinker to do work.  I think that a next step would be to investigate
that possibility, and possibly use the nr_to_scan or some other
mechanism to figure out that we're getting called multiple times and
then wait for the shrinker to make progress.  This will keep the VM from
deciding we aren't making progress and OOM'ing.

That being said this series looks good to me, you can add

Reviewed-by: Josef Bacik <josef@toxicpanda.com>

to the whole thing.  Thanks,

Josef