From: Thomas Gleixner <[email protected]>
To: Jens Axboe <[email protected]>, Ming Lei <[email protected]>
Cc: Christoph Hellwig <[email protected]>,
[email protected], [email protected],
John Garry <[email protected]>,
Bart Van Assche <[email protected]>,
Hannes Reinecke <[email protected]>,
[email protected], Peter Zijlstra <[email protected]>
Subject: Re: io_uring vs CPU hotplug, was Re: [PATCH 5/9] blk-mq: don't set data->ctx and data->hctx in blk_mq_alloc_request_hctx
Date: Thu, 21 May 2020 22:00:08 +0200 [thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
Jens Axboe <[email protected]> writes:
> Again, this is mixing up io_uring and blk-mq. Maybe it's the fact that
> both use 'ctx' that makes this confusing. On the blk-mq side, the 'ctx'
> is the per-cpu queue context, for io_uring it's the io_uring instance.
Yes, that got me horribly confused. :)
> io_sq_thread() doesn't care about any sort of percpu mappings, it's
> happy as long as it'll keep running regardless of whether or not the
> optional pinned CPU is selected and then offlined.
Fair enough.
So aside of the potential spin forever if the uring thread is lifted to
an RT scheduling class, this looks all good.
Though I assume that if that thread is pinned and an admin pushs it into
RT scheduling the spinning live lock can happen independent of cpu
hotplug.
Thanks,
tglx
next prev parent reply other threads:[~2020-05-21 20:00 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20200518093155.GB35380@T590>
[not found] ` <[email protected]>
[not found] ` <20200518115454.GA46364@T590>
[not found] ` <[email protected]>
[not found] ` <20200518141107.GA50374@T590>
[not found] ` <[email protected]>
[not found] ` <20200519015420.GA70957@T590>
[not found] ` <[email protected]>
[not found] ` <20200520011823.GA415158@T590>
[not found] ` <20200520030424.GI416136@T590>
2020-05-20 8:03 ` io_uring vs CPU hotplug, was Re: [PATCH 5/9] blk-mq: don't set data->ctx and data->hctx in blk_mq_alloc_request_hctx Christoph Hellwig
2020-05-20 14:45 ` Jens Axboe
2020-05-20 15:20 ` Jens Axboe
2020-05-20 15:31 ` Christoph Hellwig
2020-05-20 19:41 ` Thomas Gleixner
2020-05-20 20:18 ` Jens Axboe
2020-05-20 22:14 ` Thomas Gleixner
2020-05-20 22:40 ` Jens Axboe
2020-05-21 2:27 ` Ming Lei
2020-05-21 8:13 ` Thomas Gleixner
2020-05-21 9:23 ` Ming Lei
2020-05-21 18:39 ` Thomas Gleixner
2020-05-21 18:45 ` Jens Axboe
2020-05-21 20:00 ` Thomas Gleixner [this message]
2020-05-22 1:57 ` Ming Lei
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