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Message-ID: <20240402170959.GB3175858@zen.localdomain>
Date: Tue, 2 Apr 2024 10:09:59 -0700
From: Boris Burkov <boris@....io>
To: Johannes Thumshirn <jth@...nel.org>
Cc: Chris Mason <clm@...com>, Josef Bacik <josef@...icpanda.com>,
David Sterba <dsterba@...e.com>, linux-btrfs@...r.kernel.org,
linux-kernel@...r.kernel.org, Hans Holmberg <Hans.Holmberg@....com>,
Naohiro Aota <Naohiro.Aota@....com>, hch@....de,
Damien LeMoal <dlemoal@...nel.org>,
Johannes Thumshirn <johannes.thumshirn@....com>
Subject: Re: [PATCH RFC PATCH 3/3] btrfs: zoned: kick cleaner kthread if low
on space
On Thu, Mar 28, 2024 at 02:56:33PM +0100, Johannes Thumshirn wrote:
> From: Johannes Thumshirn <johannes.thumshirn@....com>
>
> Kick the cleaner kthread on chunk allocation if we're slowly running out
> of usable space on a zoned filesystem.
I'm really excited about this and think it probably makes sense on
not-zoned as well.
Have you found that this is a fast enough to help real allocations that
are in trouble? I'd be worried that it's a lot faster than waiting 30
seconds but still not urgent enough to save the day for someone trying
to allocate right now.
Not a blocking request for this patch, which I think is a definite
improvement, but we could do something like add a pass to find_free_extent
(before allocating a fresh BG?!?) that blocks on reclaim running if we
have kicked it (or errors out in a way that signals to the outer loop
that we can wait for reclaim, if needed for locking or whatever)
>
> Signed-off-by: Johannes Thumshirn <johannes.thumshirn@....com>
> ---
> fs/btrfs/zoned.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/fs/btrfs/zoned.c b/fs/btrfs/zoned.c
> index fb8707f4cab5..25c1a17873db 100644
> --- a/fs/btrfs/zoned.c
> +++ b/fs/btrfs/zoned.c
> @@ -1040,6 +1040,7 @@ int btrfs_reset_sb_log_zones(struct block_device *bdev, int mirror)
> u64 btrfs_find_allocatable_zones(struct btrfs_device *device, u64 hole_start,
> u64 hole_end, u64 num_bytes)
> {
> + struct btrfs_fs_info *fs_info = device->fs_info;
> struct btrfs_zoned_device_info *zinfo = device->zone_info;
> const u8 shift = zinfo->zone_size_shift;
> u64 nzones = num_bytes >> shift;
> @@ -1051,6 +1052,11 @@ u64 btrfs_find_allocatable_zones(struct btrfs_device *device, u64 hole_start,
> ASSERT(IS_ALIGNED(hole_start, zinfo->zone_size));
> ASSERT(IS_ALIGNED(num_bytes, zinfo->zone_size));
>
> + if (!test_bit(BTRFS_FS_CLEANER_RUNNING, &fs_info->flags) &&
> + btrfs_zoned_should_reclaim(fs_info)) {
> + wake_up_process(fs_info->cleaner_kthread);
> + }
> +
> while (pos < hole_end) {
> begin = pos >> shift;
> end = begin + nzones;
>
> --
> 2.35.3
>
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