From: Jens Axboe <[email protected]>
To: Hillf Danton <[email protected]>
Cc: Zhang Qiang <[email protected]>,
[email protected], [email protected],
Pavel Begunkov <[email protected]>,
[email protected], [email protected]
Subject: Re: Question on io-wq
Date: Thu, 22 Oct 2020 20:24:16 -0600 [thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
On 10/22/20 8:05 PM, Hillf Danton wrote:
> On Thu, 22 Oct 2020 08:08:09 -0600 Jens Axboe wrote:
>> On 10/22/20 3:02 AM, Zhang,Qiang wrote:
>>>
>>> Hi Jens Axboe
>>>
>>> There are some problem in 'io_wqe_worker' thread, when the
>>> 'io_wqe_worker' be create and Setting the affinity of CPUs in NUMA
>>> nodes, due to CPU hotplug, When the last CPU going down, the
>>> 'io_wqe_worker' thread will run anywhere. when the CPU in the node goes
>>> online again, we should restore their cpu bindings?
>>
>> Something like the below should help in ensuring affinities are
>> always correct - trigger an affinity set for an online CPU event. We
>> should not need to do it for offlining. Can you test it?
>
> CPU affinity is intact because of nothing to do on offline, and scheduler
> will move the stray workers on to the correct NUMA node if any CPU goes
> online, so it's a bit hard to see what is going to be tested.
Test it yourself:
- Boot with > 1 NUMA node
- Start an io_uring, you now get 2 workers, each affinitized to a node
- Now offline all CPUs in one node
- Online one or more of the CPU in that same node
The end result is that the worker on the node that was offlined now
has a mask of the other node, plus the newly added CPU.
So your last statement isn't correct, which is what the original
reporter stated.
--
Jens Axboe
next prev parent reply other threads:[~2020-10-23 2:24 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-22 9:02 Question on io-wq Zhang,Qiang
2020-10-22 14:08 ` Jens Axboe
2020-10-23 3:55 ` 回复: " Zhang, Qiang
2020-10-23 3:57 ` Zhang, Qiang
[not found] ` <[email protected]>
2020-10-23 2:24 ` Jens Axboe [this message]
-- strict thread matches above, loose matches on Subject: below --
2020-10-22 9:03 Zhang, Qiang
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