On Sat, Nov 26, 2022 at 04:54:46PM +0800, Yu Kuai wrote:
> Hi,
>
> 在 2022/11/18 19:30, Yu Kuai 写道:
> > From: Yu Kuai <yukuai3@xxxxxxxxxx>
> >
> > During code review, I found that 'restarts' is not useful anymore after
> > the following commits:
> >
> > 1) commit ab3cee3762e5 ("blk-mq: In blk_mq_dispatch_rq_list() "no budget"
> > is a reason to kick")
> > 2) commit d3b38596875d ("blk-mq: run queue no matter whether the request
> > is the last request")
> > 3) commit 673235f91531 ("scsi: core: Fix race between handling STS_RESOURCE
> > and completion")
> >
> > Now that if get budget ever failed, block layer will make sure to
> > trigger new run queue for the hctx. Hence there is no need to run queue
> > from scsi layer in this case.
> >
>
> Does anyone has suggestions about this patch?
>
> More info why I tried to remove this:
>
> while testing megaraid with 4 nvme with none elevator, the default
> queue_depth is 128, while I test it with fio 128 jobs and 1 iodepth,
> bw is about 4Gib/s, however, if I test with 128 jobs and 2 iodepth,
> bw is decreased to about 0.8Gib/s, and with this patch applied,
> bw can stay 4Gib/s in the later case.
I will look at this patch next week.
Can you investigate a bit the reason why perf boost is from this patch?
Thanks,
Ming
