Re: [PATCH v3] blk-throtl: optimize IOPS throttle for large IO scenarios

[brookxu.cn]

Hi Jens:

Should we apply this patch for new and older kernel ?

Thanks.

On 2021/8/10 6:39 AM, Tejun Heo wrote:
> On Mon, Aug 02, 2021 at 11:51:56AM +0800, brookxu wrote:
> > From: Chunguang Xu <brookxu@xxxxxxxxxxx>
> >
> > After patch 54efd50 (block: make generic_make_request handle
> > arbitrarily sized bios), the IO through io-throttle may be larger,
> > and these IOs may be further split into more small IOs. However,
> > IOPS throttle does not seem to be aware of this change, which
> > makes the calculation of IOPS of large IOs incomplete, resulting
> > in disk-side IOPS that does not meet expectations. Maybe we should
> > fix this problem.
> >
> > We can reproduce it by set max_sectors_kb of disk to 128, set
> > blkio.write_iops_throttle to 100, run a dd instance inside blkio
> > and use iostat to watch IOPS:
> >
> > dd if=/dev/zero of=/dev/sdb bs=1M count=1000 oflag=direct
> >
> > As a result, without this change the average IOPS is 1995, with
> > this change the IOPS is 98.
> >
> > v3: Optimize the use of atomic variables.
> > v2: Use atomic variables to solve synchronization problems.
> >
> > Signed-off-by: Chunguang Xu <brookxu@xxxxxxxxxxx>
> Acked-by: Tejun Heo <tj@xxxxxxxxxx>
>
> Thanks.