[PATCH V3 0/5] loop: improve loop aio perf by IOCB_NOWAIT

Ming Lei
2025-03-22T01:26:36Z

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/a8e5c76a-231f-07d1-a394-847de930f638@redhat.com/

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

Thanks,
Ming

V3:
- add reviewed-by tag
- rename variable & improve commit log & comment on 5/5(Christoph)

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 | 227 ++++++++++++++++++++++++++++++++++---------
1 file changed, 181 insertions(+), 46 deletions(-)

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2.47.0