diff options
| author | Naohiro Aota <naohiro.aota@wdc.com> | 2024-02-05 16:01:16 +0300 |
|---|---|---|
| committer | David Sterba <dsterba@suse.com> | 2024-03-04 18:24:52 +0300 |
| commit | 2761ece8935fbf2fddb8daad0b9f11c045a922f4 (patch) | |
| tree | 9d35b7094e18f1c3bc44e043ee8b6891a1029778 /fs/btrfs/bio.c | |
| parent | b2324e08b8b3b38bb86ba779970b0caab32ef0ed (diff) | |
| download | linux-2761ece8935fbf2fddb8daad0b9f11c045a922f4.tar.xz | |
btrfs: introduce offload_csum_mode to tweak checksum offloading behavior
We disable offloading checksum to workqueues and do it synchronously when
the checksum algorithm is fast. However, as reported in the link below,
RAID0 with multiple devices may suffer from the sync checksum, because
"fast checksum" is still not fast enough to catch up with RAID0 writing.
We don't have an effective way to determine whether to offload or not,
for now add a sysfs knob so this can be debugged. This is intentionally
under CONFIG_BTRFS_DEBUG so ti's not exposed to users as it may be
removed in the future agin.
Introduce fs_devices->offload_csum_mode, so that a btrfs developer can
change the behavior by writing to /sys/fs/btrfs/<uuid>/offload_csum. The
default is "auto" which is the same as the previous behavior. Or, you
can set "on" or "off" (or "y" or "n" whatever kstrtobool() accepts) to
always/never offload checksum.
More benchmark need to be collected with this knob to implement a proper
criteria to enable/disable checksum offloading.
Link: https://lore.kernel.org/linux-btrfs/20230731152223.4EFB.409509F4@e16-tech.com/
Link: https://lore.kernel.org/linux-btrfs/p3vo3g7pqn664mhmdhlotu5dzcna6vjtcoc2hb2lsgo2fwct7k@xzaxclba5tae/
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Diffstat (limited to 'fs/btrfs/bio.c')
| -rw-r--r-- | fs/btrfs/bio.c | 14 |
1 files changed, 13 insertions, 1 deletions
diff --git a/fs/btrfs/bio.c b/fs/btrfs/bio.c index 960b81718e29..477f350a8bd0 100644 --- a/fs/btrfs/bio.c +++ b/fs/btrfs/bio.c @@ -608,8 +608,20 @@ static void run_one_async_done(struct btrfs_work *work, bool do_free) static bool should_async_write(struct btrfs_bio *bbio) { + bool auto_csum_mode = true; + +#ifdef CONFIG_BTRFS_DEBUG + struct btrfs_fs_devices *fs_devices = bbio->fs_info->fs_devices; + enum btrfs_offload_csum_mode csum_mode = READ_ONCE(fs_devices->offload_csum_mode); + + if (csum_mode == BTRFS_OFFLOAD_CSUM_FORCE_OFF) + return false; + + auto_csum_mode = (csum_mode == BTRFS_OFFLOAD_CSUM_AUTO); +#endif + /* Submit synchronously if the checksum implementation is fast. */ - if (test_bit(BTRFS_FS_CSUM_IMPL_FAST, &bbio->fs_info->flags)) + if (auto_csum_mode && test_bit(BTRFS_FS_CSUM_IMPL_FAST, &bbio->fs_info->flags)) return false; /* |