| Message ID | 20230720181310.71589-8-axboe@kernel.dk (mailing list archive) |
|---|---|
| State | Deferred, archived |
| Headers | show |
| Series | Improve async iomap DIO performance | expand |
Looks good:
Reviewed-by: Christoph Hellwig <hch@lst.de>
On Thu, Jul 20, 2023 at 12:13:09PM -0600, Jens Axboe wrote: > If the filesystem dio handler understands IOCB_DIO_DEFER, we'll get > a kiocb->ki_complete() callback with kiocb->dio_complete set. In that > case, rather than complete the IO directly through task_work, queue > up an intermediate task_work handler that first processes this > callback and then immediately completes the request. > > For XFS, this avoids a punt through a workqueue, which is a lot less > efficient and adds latency to lower queue depth (or sync) O_DIRECT > writes. > > Only do this for non-polled IO, as polled IO doesn't need this kind > of deferral as it always completes within the task itself. This then > avoids a check for deferral in the polled IO completion handler. > > Signed-off-by: Jens Axboe <axboe@kernel.dk> Seems pretty obvious to me, though I'm famous for not being an experienced io_uring user yet... Reviewed-by: Darrick J. Wong <djwong@kernel.org> --D > --- > io_uring/rw.c | 27 ++++++++++++++++++++++++--- > 1 file changed, 24 insertions(+), 3 deletions(-) > > diff --git a/io_uring/rw.c b/io_uring/rw.c > index 1bce2208b65c..f4f700383b4e 100644 > --- a/io_uring/rw.c > +++ b/io_uring/rw.c > @@ -285,6 +285,14 @@ static inline int io_fixup_rw_res(struct io_kiocb *req, long res) > > void io_req_rw_complete(struct io_kiocb *req, struct io_tw_state *ts) > { > + struct io_rw *rw = io_kiocb_to_cmd(req, struct io_rw); > + > + if (rw->kiocb.dio_complete) { > + long res = rw->kiocb.dio_complete(rw->kiocb.private); > + > + io_req_set_res(req, io_fixup_rw_res(req, res), 0); > + } > + > io_req_io_end(req); > > if (req->flags & (REQ_F_BUFFER_SELECTED|REQ_F_BUFFER_RING)) { > @@ -300,9 +308,11 @@ static void io_complete_rw(struct kiocb *kiocb, long res) > struct io_rw *rw = container_of(kiocb, struct io_rw, kiocb); > struct io_kiocb *req = cmd_to_io_kiocb(rw); > > - if (__io_complete_rw_common(req, res)) > - return; > - io_req_set_res(req, io_fixup_rw_res(req, res), 0); > + if (!rw->kiocb.dio_complete) { > + if (__io_complete_rw_common(req, res)) > + return; > + io_req_set_res(req, io_fixup_rw_res(req, res), 0); > + } > req->io_task_work.func = io_req_rw_complete; > __io_req_task_work_add(req, IOU_F_TWQ_LAZY_WAKE); > } > @@ -916,6 +926,17 @@ int io_write(struct io_kiocb *req, unsigned int issue_flags) > } > kiocb->ki_flags |= IOCB_WRITE; > > + /* > + * For non-polled IO, set IOCB_DIO_DEFER, stating that our handler > + * groks deferring the completion to task context. This isn't > + * necessary and useful for polled IO as that can always complete > + * directly. > + */ > + if (!(kiocb->ki_flags & IOCB_HIPRI)) { > + kiocb->ki_flags |= IOCB_DIO_DEFER; > + kiocb->dio_complete = NULL; > + } > + > if (likely(req->file->f_op->write_iter)) > ret2 = call_write_iter(req->file, kiocb, &s->iter); > else if (req->file->f_op->write) > -- > 2.40.1
On 7/21/23 9:50?AM, Darrick J. Wong wrote: > On Thu, Jul 20, 2023 at 12:13:09PM -0600, Jens Axboe wrote: >> If the filesystem dio handler understands IOCB_DIO_DEFER, we'll get >> a kiocb->ki_complete() callback with kiocb->dio_complete set. In that >> case, rather than complete the IO directly through task_work, queue >> up an intermediate task_work handler that first processes this >> callback and then immediately completes the request. >> >> For XFS, this avoids a punt through a workqueue, which is a lot less >> efficient and adds latency to lower queue depth (or sync) O_DIRECT >> writes. >> >> Only do this for non-polled IO, as polled IO doesn't need this kind >> of deferral as it always completes within the task itself. This then >> avoids a check for deferral in the polled IO completion handler. >> >> Signed-off-by: Jens Axboe <axboe@kernel.dk> > > Seems pretty obvious to me, though I'm famous for not being an > experienced io_uring user yet... > > Reviewed-by: Darrick J. Wong <djwong@kernel.org> Thanks, keyword here is "yet" ;-)
diff --git a/io_uring/rw.c b/io_uring/rw.c index 1bce2208b65c..f4f700383b4e 100644 --- a/io_uring/rw.c +++ b/io_uring/rw.c @@ -285,6 +285,14 @@ static inline int io_fixup_rw_res(struct io_kiocb *req, long res) void io_req_rw_complete(struct io_kiocb *req, struct io_tw_state *ts) { + struct io_rw *rw = io_kiocb_to_cmd(req, struct io_rw); + + if (rw->kiocb.dio_complete) { + long res = rw->kiocb.dio_complete(rw->kiocb.private); + + io_req_set_res(req, io_fixup_rw_res(req, res), 0); + } + io_req_io_end(req); if (req->flags & (REQ_F_BUFFER_SELECTED|REQ_F_BUFFER_RING)) { @@ -300,9 +308,11 @@ static void io_complete_rw(struct kiocb *kiocb, long res) struct io_rw *rw = container_of(kiocb, struct io_rw, kiocb); struct io_kiocb *req = cmd_to_io_kiocb(rw); - if (__io_complete_rw_common(req, res)) - return; - io_req_set_res(req, io_fixup_rw_res(req, res), 0); + if (!rw->kiocb.dio_complete) { + if (__io_complete_rw_common(req, res)) + return; + io_req_set_res(req, io_fixup_rw_res(req, res), 0); + } req->io_task_work.func = io_req_rw_complete; __io_req_task_work_add(req, IOU_F_TWQ_LAZY_WAKE); } @@ -916,6 +926,17 @@ int io_write(struct io_kiocb *req, unsigned int issue_flags) } kiocb->ki_flags |= IOCB_WRITE; + /* + * For non-polled IO, set IOCB_DIO_DEFER, stating that our handler + * groks deferring the completion to task context. This isn't + * necessary and useful for polled IO as that can always complete + * directly. + */ + if (!(kiocb->ki_flags & IOCB_HIPRI)) { + kiocb->ki_flags |= IOCB_DIO_DEFER; + kiocb->dio_complete = NULL; + } + if (likely(req->file->f_op->write_iter)) ret2 = call_write_iter(req->file, kiocb, &s->iter); else if (req->file->f_op->write)
If the filesystem dio handler understands IOCB_DIO_DEFER, we'll get a kiocb->ki_complete() callback with kiocb->dio_complete set. In that case, rather than complete the IO directly through task_work, queue up an intermediate task_work handler that first processes this callback and then immediately completes the request. For XFS, this avoids a punt through a workqueue, which is a lot less efficient and adds latency to lower queue depth (or sync) O_DIRECT writes. Only do this for non-polled IO, as polled IO doesn't need this kind of deferral as it always completes within the task itself. This then avoids a check for deferral in the polled IO completion handler. Signed-off-by: Jens Axboe <axboe@kernel.dk> --- io_uring/rw.c | 27 ++++++++++++++++++++++++--- 1 file changed, 24 insertions(+), 3 deletions(-)