On Thu, Sep 8, 2022 at 1:26 AM Stefan Roesch <shr@xxxxxx> 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: > For fio the following results have been obtained with a queue depth of > 1 and 4k block size (runtime 600 secs): > > sequential writes: > without patch with patch libaio psync > iops: 55k 134k 117K 148K > bw: 221MB/s 538MB/s 469MB/s 592MB/s > clat: 15286ns 82ns 994ns 6340ns This is very interesting information to not have in the git history, specially because it's exactly this that motivates all the patches. I suggest adding this to the changelog of the last patch, and then mention that those results are the result of comparing a branch with the patchset versus one without it, also mentioning the subject of all the patches that belong to the patchset. It should also mention how to run the test: i.e. the fio command line or config file, so that it's clear to everyone all the details and how to reproduce the results. The patchset overall looks good to me, I just left a few comments on most of the individual patches, all minor things. Thanks. > > > For an io depth of 1, 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. To achieve the > same or better performance with the exisiting code an io depth of 4 is required. > Increasing the iodepth further does not lead to improvements. > > > 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: > > 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: btrfs: plumb NOWAIT through the write path > btrfs: make balance_dirty_pages nowait compatible > btrfs: add assert to search functions > btrfs: enable nowait async buffered writes > > fs/btrfs/block-group.c | 2 +- > fs/btrfs/ctree.c | 48 ++++++++++++++- > 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, 239 insertions(+), 59 deletions(-) > > > base-commit: 53e99dcff61e1523ec1c3628b2d564ba15d32eb7 > -- > 2.30.2 >
