On 2/17/23 7:27 AM, Pankaj Raghav wrote: > Hi Jens, > > On 2023-02-16 05:08, Jens Axboe wrote: > >> I think your numbers are skewed because brd isn't flagg nowait, can you >> try with this? >> >> I ran some quick testing here, using the current tree: >> >> without patch with patch >> io_uring ~430K IOPS ~3.4M IOPS >> libaio ~895K IOPS ~895K IOPS >> >> which is a pretty substantial difference... >> > > I rebased my blk-mq changes on top of your nowait patches, but still I see a > regression with blk-mq. When I tried to trace and run perf, nothing odd > stood out, except for the normal blk-mq overhead. > > Could you try it in your setup and see if you are noticing a similar trend? > Because based on the numbers you shared yesterday, I didn't see this regression. > > fio script I run to benchmark: > > $ fio --name=<workload> --rw=<workload> --ramp_time=5s --size=1G > --io_size=10G --loop=4 --cpus_allowed=1 --filename=/dev/ram0 --direct=1 > --iodepth=128 --ioengine=<engine> > > +-----------+-----------+--------+--------+ > | io_uring | bio(base) | blk-mq | delta | > +-----------+-----------+--------+--------+ > | read | 577 | 446 | -22.7 | > | randread | 504 | 416 | -17.46 | > | write | 554 | 424 | -23.47 | > | randwrite | 484 | 381 | -21.28 | > +-----------+-----------+--------+--------+ > > +-----------+-----------+--------+--------+ > | libaio | bio(base) | blk-mq | delta | > +-----------+-----------+--------+--------+ > | read | 412 | 341 | -17.23 | > | randread | 389 | 335 | -13.88 | > | write | 401 | 329 | -17.96 | > | randwrite | 351 | 304 | -13.39 | > +-----------+-----------+--------+--------+ This is pretty much expected, as blk-mq adds a bunch of things that brd doesn't really care about. One example of such would be tag management. My reaction to your initial report wasn't a surprise that blk-mq would be slower than bio based for this use case, rather that io_uring was slower than libaio. -- Jens Axboe
