Re: [PATCH v3 00/12] io-uring/btrfs: support async buffered writes

[Filipe Manana <fdmanana@kernel.org>]

On Mon, Sep 12, 2022 at 8:28 PM Stefan Roesch <shr@fb.com> wrote:
>
> This patch series adds support for async buffered writes when using both
> btrfs and io-uring. Currently io-uring only supports buffered writes (for btrfs)
> in the slow path, by processing them in the io workers. With this patch series
> it is now possible to support buffered writes in the fast path. To be able to use
> the fast path, the required pages must be in the page cache, the required locks
> in btrfs can be granted immediately and no additional blocks need to be read
> form disk.
>
> This patch series makes use of the changes that have been introduced by a
> previous patch series: "io-uring/xfs: support async buffered writes"
>
> Performance results:
>
> The new patch improves throughput by over two times (compared to the exiting
> behavior, where buffered writes are processed by an io-worker process) and also
> the latency is considerably reduced. Detailled results are part of the changelog
> of the first commit.

Not in the first, but in the last commit instead.

Looks fine to me now, thanks.

Reviewed-by: Filipe Manana <fdmanana@suse.com>


>
>
> BTRFS changes:
>  -Add option for NOWAIT IOCB's to tell that searches do not wait on locks. This
>   adds the nowait option to btrfs_path.
>  -For NOWAIT buffered writes on PREALLOC or NOCOW extents tell can_nocow_extent()
>   that we don't want to wait on any locks or metadata IO.
>  -Support no_flush reservations for nowait buffered writes.
>  -Add btrfs_try_lock_ordered_range() function.
>  -Add nowait flag to btrfs_check_nocow_lock() to use it in write code path.
>  -Add nowait parameter to prepare_pages() function.
>  -Plumb nowait through the write code path.
>  -Enable nowait buffered writes.
>
>
> Testing:
>   This patch has been tested with xfstests, fsx, fio. xfstests shows no new
>   diffs compared to running without the patch series.
>
>
> Changes:
>
> V3:
>  - Updated changelog of "btrfs: implement a nowait option for tree searches"
>    to say -EAGAIN.
>  - Use bool return value in signature of btrfs_try_lock_ordered_range
>  - Renamed variable tmp to can_nocow in btrfs_buffered_write
>  - Fixed coding style in get_prepare_fgp_flags
>  - Set pages[i] to NULL in error code path of lock_and_cleanup_extent_if_need()
>  - Added const in definition of "bool nowait"
>  - Removed unlikely from btrfs_buffered_write
>  - Rephrased changelog for "btrfs: add assert to search functions" and used
>    asserts instead of warnings
>  - Explained why enocded writes are not supported in the changelog
>  - Moved performance results to changelog of first commit
>
> V2:
>  - Replace EWOULDBLOCK with EAGAIN. In Version 1 it was not used consistently
>  - Export function balance_dirty_pages_ratelimited_flags()
>  - Add asserts/warnings for search functions when nowait is set, but we don't
>    expect that they are invoked with nowait set.
>
>
>
> Josef Bacik (5):
>   btrfs: implement a nowait option for tree searches
>   btrfs: make can_nocow_extent nowait compatible
>   btrfs: add the ability to use NO_FLUSH for data reservations
>   btrfs: add btrfs_try_lock_ordered_range
>   btrfs: make btrfs_check_nocow_lock nowait compatible
>
> Stefan Roesch (7):
>   mm: export balance_dirty_pages_ratelimited_flags()
>   btrfs: make prepare_pages nowait compatible
>   btrfs: make lock_and_cleanup_extent_if_need nowait compatible
>   btrfs: plumb NOWAIT through the write path
>   btrfs: make balance_dirty_pages nowait compatible
>   btrfs: assert nowait mode is not used for some btree search functions
>   btrfs: enable nowait async buffered writes
>
>  fs/btrfs/block-group.c    |   2 +-
>  fs/btrfs/ctree.c          |  43 ++++++++++++-
>  fs/btrfs/ctree.h          |   8 ++-
>  fs/btrfs/delalloc-space.c |  13 +++-
>  fs/btrfs/delalloc-space.h |   3 +-
>  fs/btrfs/extent-tree.c    |   5 ++
>  fs/btrfs/file-item.c      |   4 +-
>  fs/btrfs/file.c           | 124 ++++++++++++++++++++++++++++----------
>  fs/btrfs/inode.c          |  22 ++++---
>  fs/btrfs/locking.c        |  23 +++++++
>  fs/btrfs/locking.h        |   1 +
>  fs/btrfs/ordered-data.c   |  28 +++++++++
>  fs/btrfs/ordered-data.h   |   1 +
>  fs/btrfs/relocation.c     |   2 +-
>  fs/btrfs/scrub.c          |   4 +-
>  fs/btrfs/space-info.c     |   3 +-
>  fs/btrfs/tree-log.c       |   6 +-
>  mm/page-writeback.c       |   1 +
>  18 files changed, 234 insertions(+), 59 deletions(-)
>
>
> base-commit: 80e78fcce86de0288793a0ef0f6acf37656ee4cf
> --
> 2.30.2
>