| Message ID | 647e79f4-ddaa-7003-6e00-f31e11535082@kernel.dk (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [GIT,PULL] Improve iomap async dio performance | expand |
On Fri, Jul 21, 2023 at 10:54:41AM -0600, Jens Axboe wrote: > Hi, > > Here's the pull request for improving async dio performance with > iomap. Contains a few generic cleanups as well, but the meat of it > is described in the tagged commit message below. > > Please pull for 6.6! Ah, I just reviewed v4 (v5 came out while I was sleeping) and I think there are still problems with some of the logic... So it might be worth holding off from pulling this until we work through that... -Dave.
On Sat, Jul 22, 2023 at 08:08:51AM +1000, Dave Chinner wrote: > On Fri, Jul 21, 2023 at 10:54:41AM -0600, Jens Axboe wrote: > > Hi, > > > > Here's the pull request for improving async dio performance with > > iomap. Contains a few generic cleanups as well, but the meat of it > > is described in the tagged commit message below. > > > > Please pull for 6.6! > > Ah, I just reviewed v4 (v5 came out while I was sleeping) and I > think there are still problems with some of the logic... > > So it might be worth holding off from pulling this until we work > through that... No worries, next week I'm starting the iomap merging process with willy's large folios write (Monday) and then Ritesh's dirty tracking (Tuesday if nothing blows up), so there's plenty of time for more questions. --D > -Dave. > -- > Dave Chinner > david@fromorbit.com
On 7/21/23 4:08?PM, Dave Chinner wrote: > On Fri, Jul 21, 2023 at 10:54:41AM -0600, Jens Axboe wrote: >> Hi, >> >> Here's the pull request for improving async dio performance with >> iomap. Contains a few generic cleanups as well, but the meat of it >> is described in the tagged commit message below. >> >> Please pull for 6.6! > > Ah, I just reviewed v4 (v5 came out while I was sleeping) and I > think there are still problems with some of the logic... > > So it might be worth holding off from pulling this until we work > through that... No problem, thanks for taking a look! I'll address your feedback tomorrow and I can always just send another pull request.
Hi, Here's the pull request for improving async dio performance with iomap. Contains a few generic cleanups as well, but the meat of it is described in the tagged commit message below. Please pull for 6.6! The following changes since commit ccff6d117d8dc8d8d86e8695a75e5f8b01e573bf: Merge tag 'perf-tools-fixes-for-v6.5-1-2023-07-18' of git://git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools (2023-07-18 14:51:29 -0700) are available in the Git repository at: git://git.kernel.dk/linux.git tags/xfs-async-dio for you to fetch changes up to 901a0c0e4248aa7e3ab4dce9a8c67c47215e6ccc: iomap: use an unsigned type for IOMAP_DIO_* defines (2023-07-21 10:34:42 -0600) ---------------------------------------------------------------- iomap always punts async dio write completions to a workqueue, which has a cost in terms of efficiency (now you need an unrelated worker to process it) and latency (now you're bouncing a completion through an async worker, which is a classic slowdown scenario). Even for writes that should, in theory, be able to complete inline, if we race with truncate or need to invalidate pages post completion, we cannot sanely be in IRQ context as the locking types don't allow for that. io_uring handles IRQ completions via task_work, and for writes that don't need to do extra IO at completion time, we can safely complete them inline from that. This patchset adds IOCB_DIO_CALLER_COMP, which an IO issuer can set to inform the completion side that any extra work that needs doing for that completion can be punted to a safe task context. The iomap dio completion will happen in hard/soft irq context, and we need a saner context to process these completions. IOCB_DIO_CALLER_COMP is added, which can be set in a struct kiocb->ki_flags by the issuer. If the completion side of the iocb handling understands this flag, it can choose to set a kiocb->dio_complete() handler and just call ki_complete from IRQ context. The issuer must then ensure that this callback is processed from a task. io_uring punts IRQ completions to task_work already, so it's trivial wire it up to run more of the completion before posting a CQE. This is good for up to a 37% improvement in throughput/latency for low queue depth IO, patch 5 has the details. If we need to do real work at completion time, iomap will clear the IOMAP_DIO_CALLER_COMP flag. This work came about when Andres tested low queue depth dio writes for postgres and compared it to doing sync dio writes, showing that the async processing slows us down a lot. ---------------------------------------------------------------- Jens Axboe (9): iomap: cleanup up iomap_dio_bio_end_io() iomap: add IOMAP_DIO_INLINE_COMP iomap: treat a write through cache the same as FUA iomap: completed polled IO inline iomap: only set iocb->private for polled bio fs: add IOCB flags related to passing back dio completions io_uring/rw: add write support for IOCB_DIO_CALLER_COMP iomap: support IOCB_DIO_CALLER_COMP iomap: use an unsigned type for IOMAP_DIO_* defines fs/iomap/direct-io.c | 166 +++++++++++++++++++++++++++++++++++++++------------ include/linux/fs.h | 35 ++++++++++- io_uring/rw.c | 26 +++++++- 3 files changed, 183 insertions(+), 44 deletions(-)