On Thu, Feb 04, 2021 at 05:35:02AM -0600, Mike Christie wrote: > The following patches made over Martin's 5.12 branches fix two > issues: > > 1. target_core_iblock plugs and unplugs the queue for every > command. To handle this issue and handle an issue that > vhost-scsi and loop were avoiding by adding their own workqueue, > I added a new submission workqueue to LIO. Drivers can pass cmds > to it, and we can then submit batches of cmds. > > 2. vhost-scsi and loop on the submission side were doing a work > per cmd and on the lio completion side it was doing a work per > cmd. The cap on running works is 512 (max_active) and so we can > end up end up using a lot of threads when submissions start blocking > because they hit the block tag limit or the completion side blocks > trying to send the cmd. In this patchset I just use a cmd list > per session to avoid abusing the workueue layer. > > The combined patchset fixes a major perf issue we've been hitting > where IOPs is stuck at 230K when running: > > fio --filename=/dev/sda --direct=1 --rw=randrw --bs=4k > --ioengine=libaio --iodepth=128 --numjobs=8 --time_based > --group_reporting --runtime=60 > > The patches in this set get me to 350K when using devices that > have native IOPs of around 400-500K. > > Note that 5.12 has some interrupt changes that my patches > collide with. Martin's 5.12 branches had the changes so I > based my patches on that. For vhost-scsi: Reviewed-by: Stefan Hajnoczi <stefanha@xxxxxxxxxx>
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