[V2,0/5] loop: improve loop aio perf by IOCB_NOWAIT

Message

Ming Lei March 14, 2025, 2:11 a.m. UTC

Hello Jens,

This patchset improves loop aio perf by using IOCB_NOWAIT for avoiding to queue aio
command to workqueue context, meantime refactor lo_rw_aio() a bit.

In my test VM, loop disk perf becomes very close to perf of the backing block
device(nvme/mq virtio-scsi).

And Mikulas verified that this way can improve 12jobs sequential rw io by
~5X, and basically solve the reported problem together with loop MQ change.

https://lore.kernel.org/linux-block/[e-mail]/

The loop MQ change will be posted as standalone patch, because it needs
losetup change.


Thanks,
Ming

V2:
	- patch style fix & cleanup (Christoph)
	- fix randwrite perf regression on sparse backing file
	- drop MQ change

Ming Lei (5):
  loop: simplify do_req_filebacked()
  loop: cleanup lo_rw_aio()
  loop: move command blkcg/memcg initialization into loop_queue_work
  loop: try to handle loop aio command via NOWAIT IO first
  loop: add hint for handling aio via IOCB_NOWAIT

 drivers/block/loop.c | 232 ++++++++++++++++++++++++++++++++++---------
 1 file changed, 186 insertions(+), 46 deletions(-)

Comments

Ming Lei March 14, 2025, 2:16 a.m. UTC | #1

On Fri, Mar 14, 2025 at 10:12 AM Ming Lei <[e-mail]> wrote:
>
> Hello Jens,
>
> This patchset improves loop aio perf by using IOCB_NOWAIT for avoiding to queue aio
> command to workqueue context, meantime refactor lo_rw_aio() a bit.
>
> In my test VM, loop disk perf becomes very close to perf of the backing block
> device(nvme/mq virtio-scsi).
>
> And Mikulas verified that this way can improve 12jobs sequential rw io by
> ~5X, and basically solve the reported problem together with loop MQ change.
>
> https://lore.kernel.org/linux-block/[e-mail]/
>
> The loop MQ change will be posted as standalone patch, because it needs
> losetup change.
>
>
> Thanks,
> Ming
>
> V2:
>         - patch style fix & cleanup (Christoph)
>         - fix randwrite perf regression on sparse backing file
>         - drop MQ change

Hi Mikulas,

Just realized that you are missing in Cc list and loop you in, sorry for that...

Thanks,