iomap: support IOCB_DIO_DEFER
If IOCB_DIO_DEFER is set, utilize that to set kiocb->dio_complete handler
and data for that callback. Rather than punt the completion to a
workqueue, we pass back the handler and data to the issuer and will get a
callback from a safe task context.
Using the following fio job to randomly dio write 4k blocks at
queue depths of 1..16:
fio --name=dio-write --filename=/data1/file --time_based=1 \
--runtime=10 --bs=4096 --rw=randwrite --norandommap --buffered=0 \
--cpus_allowed=4 --ioengine=io_uring --iodepth=16
shows the following results before and after this patch:
Stock Patched Diff
=======================================
QD1 155K 162K + 4.5%
QD2 290K 313K + 7.9%
QD4 533K 597K +12.0%
QD8 604K 827K +36.9%
QD16 615K 845K +37.4%
which shows nice wins all around. If we factored in per-IOP efficiency,
the wins look even nicer. This becomes apparent as queue depth rises,
as the offloaded workqueue completions runs out of steam.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
1 file changed
