Re: [External] Re: [PATCH] io_uring: add IORING_SETUP_NO_SQTHREAD_STATS flag to disable sqthread stats collection.

[Fengnan Chang <changfengnan@bytedance.com>]

Xiaobing Li <xiaobing.li@samsung.com> 于2025年10月17日周五 17:18写道：
>
> On 10/16/25 20:09, Fengnan Chang wrote:
> >On 10/16/25 20:03, Pavel Begunkov wrote：
> >>
> >> On 10/16/25 12:45, Fengnan Chang wrote:
> >> > introduces a new flag IORING_SETUP_NO_SQTHREAD_STATS that allows
> >> > user to disable the collection of statistics in the sqthread.
> >> > When this flag is set, the getrusage() calls in the sqthread are
> >> > skipped, which can provide a small performance improvement in high
> >> > IOPS workloads.
> >>
> >> It was added for dynamically adjusting SQPOLL timeouts, at least that
> >> what the author said, but then there is only the fdinfo to access it,
> >> which is slow and unreliable, and no follow up to expose it in a
> >> better way. To be honest, I have serious doubts it has ever been used,
> >> and I'd be tempted to completely remove it out of the kernel. Fdinfo
> >> format wasn't really stable for io_uring and we can leave it printing
> >> some made up values like 100% util.
> >
> >Agree,  IMO turning off stats by default would be a better approach, but
> >I'm concerned that some people are using this in fdinfo. I'd like to hear
> >the author's opinion.
>
> We use fdinfo statistics to evaluate some of our internal test data.
> Initially, I tested the performance impact of adding this feature, and the
> results showed that it had little impact on performance. Therefore,
> I didn't consider adding a switch to control its use. However,
> adding a switch to control whether to enable utilization statistics
> is a good idea.

Get, I think we have a common understanding to turn off stats by default
and add flags to turn them on. I'll send patch V2 to do this.
>
> --
> Xiaobing Li