From: Pavel Begunkov <[email protected]>
To: Hao Xu <[email protected]>, Jens Axboe <[email protected]>
Cc: [email protected], Joseph Qi <[email protected]>
Subject: Re: [PATCH RFC 5.13 1/2] io_uring: add support for ns granularity of io_sq_thread_idle
Date: Wed, 29 Sep 2021 12:37:34 +0100 [thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
On 9/29/21 10:24 AM, Hao Xu wrote:
> 在 2021/9/28 下午6:51, Pavel Begunkov 写道:
>> On 9/26/21 11:00 AM, Hao Xu wrote:
[...]
>>> I'm gonna pick this one up again, currently this patch
>>> with ktime_get_ns() works good on our productions. This
>>> patch makes the latency a bit higher than before, but
>>> still lower than aio.
>>> I haven't gotten a faster alternate for ktime_get_ns(),
>>> any hints?
>>
>> Good, I'd suggest to look through Documentation/core-api/timekeeping.rst
>> In particular coarse variants may be of interest.
>> https://www.kernel.org/doc/html/latest/core-api/timekeeping.html#coarse-and-fast-ns-access
>>
> The coarse functions seems to be like jiffies, because they use the last
> timer tick(from the explanation in that doc, it seems the timer tick is
> in the same frequency as jiffies update). So I believe it is just
> another format of jiffies which is low accurate.
I haven't looked into the details, but it seems that unlike jiffies for
the coarse mode 10ms (or whatever) is the worst case, but it _may_ be
much better on average and feasible for your case, but can't predict
if that's really the case in a real system and what will be the
relative error comparing to normal ktime_ns().
--
Pavel Begunkov
next prev parent reply other threads:[~2021-09-29 11:38 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-28 13:32 [PATCH RFC 5.13 0/2] adaptive sqpoll and its wakeup optimization Hao Xu
2021-04-28 13:32 ` [PATCH RFC 5.13 1/2] io_uring: add support for ns granularity of io_sq_thread_idle Hao Xu
2021-04-28 14:07 ` Pavel Begunkov
2021-04-28 14:16 ` Jens Axboe
2021-04-28 14:53 ` Pavel Begunkov
2021-04-28 14:54 ` Jens Axboe
2021-04-29 3:41 ` Hao Xu
2021-04-29 9:11 ` Pavel Begunkov
2021-05-05 14:07 ` Hao Xu
2021-05-05 17:40 ` Pavel Begunkov
2021-04-29 3:28 ` Hao Xu
2021-04-29 22:15 ` Pavel Begunkov
2021-09-26 10:00 ` Hao Xu
2021-09-28 10:51 ` Pavel Begunkov
2021-09-29 7:52 ` Hao Xu
2021-09-29 9:24 ` Hao Xu
2021-09-29 11:37 ` Pavel Begunkov [this message]
2021-09-29 12:13 ` Hao Xu
2021-09-30 8:51 ` Pavel Begunkov
2021-09-30 12:04 ` Pavel Begunkov
2021-10-05 15:00 ` Hao Xu
2021-04-28 13:32 ` [PATCH RFC 5.13 2/2] io_uring: submit sqes in the original context when waking up sqthread Hao Xu
2021-04-28 14:12 ` Jens Axboe
2021-04-29 4:12 ` Hao Xu
2021-04-28 14:34 ` Pavel Begunkov
2021-04-28 14:37 ` Pavel Begunkov
2021-04-29 4:37 ` Hao Xu
2021-04-29 9:28 ` Pavel Begunkov
2021-05-05 11:20 ` Hao Xu
2021-04-28 14:39 ` Jens Axboe
2021-04-28 14:50 ` Pavel Begunkov
2021-04-28 14:53 ` Jens Axboe
2021-04-28 14:56 ` Pavel Begunkov
2021-04-28 15:09 ` Jens Axboe
2021-04-29 4:43 ` Hao Xu
2021-04-29 8:44 ` Hao Xu
2021-04-29 22:10 ` Pavel Begunkov
2021-05-05 13:10 ` Hao Xu
2021-05-05 17:44 ` Pavel Begunkov
2021-04-29 22:02 ` Pavel Begunkov
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