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SubjectRe: [PATCH RESEND v4] fs/epoll: Remove unnecessary wakeups of nested epoll that in ET mode
On 2019-09-28 04:29, Andrew Morton wrote:
> On Wed, 25 Sep 2019 09:56:03 +0800 hev <r@hev.cc> wrote:
>
>> From: Heiher <r@hev.cc>
>>
>> Take the case where we have:
>>
>> t0
>> | (ew)
>> e0
>> | (et)
>> e1
>> | (lt)
>> s0
>>
>> t0: thread 0
>> e0: epoll fd 0
>> e1: epoll fd 1
>> s0: socket fd 0
>> ew: epoll_wait
>> et: edge-trigger
>> lt: level-trigger
>>
>> We only need to wakeup nested epoll fds if something has been queued
>> to the
>> overflow list, since the ep_poll() traverses the rdllist during
>> recursive poll
>> and thus events on the overflow list may not be visible yet.
>>
>> Test code:
>
> Look sane to me. Do you have any performance testing results which
> show a benefit?
>
> epoll maintainership isn't exactly a hive of activity nowadays :(
> Roman, would you please have time to review this?

Yes, I can revisit this once more next week.

Heiher, mind to prepare a patchset with your test suit and make it a
part
of kselftest? I hope nobody has any objections.

--
Roman

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