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

[Fengnan Chang <changfengnan@bytedance.com>]

Pavel Begunkov <asml.silence@gmail.com> 于2025年10月16日周四 20:03写道：
>
> 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.

>
> If it's there for outside monitoring, that should be done with bpf,
> with maybe additional tracepoints.
>
> --
> Pavel Begunkov
>