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

[Xiaobing Li <xiaobing.li@samsung.com>]

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.

--
Xiaobing Li