From: Keith Busch <kbusch@kernel.org>
To: Jens Axboe <axboe@kernel.dk>
Cc: Keith Busch <keith.busch@intel.com>,
linux-block@vger.kernel.org, linux-nvme@lists.infradead.org,
Jianchao Wang <jianchao.w.wang@oracle.com>,
Bart Van Assche <bvanassche@acm.org>,
Ming Lei <ming.lei@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH] blk-mq: Wait for for hctx requests on CPU unplug
Date: Fri, 5 Apr 2019 16:37:20 -0600 [thread overview]
Message-ID: <20190405223719.GC25081@localhost.localdomain> (raw)
In-Reply-To: <226503cd-53ac-902c-7944-b2748407b1d3@kernel.dk>
On Fri, Apr 05, 2019 at 04:23:27PM -0600, Jens Axboe wrote:
> On 4/5/19 3:59 PM, Keith Busch wrote:
> > Managed interrupts can not migrate affinity when their CPUs are offline.
> > If the CPU is allowed to shutdown before they're returned, commands
> > dispatched to managed queues won't be able to complete through their
> > irq handlers.
> >
> > Introduce per-hctx reference counting so we can block the CPU dead
> > notification for all allocated requests to complete if an hctx's last
> > CPU is being taken offline.
>
> What does this do to performance? We're doing a map per request...
It should be the same cost as the blk_queue_enter/blk_queue_exit that's
also done per request, which is pretty cheap way to count users. I
don't think I'm measuring a difference, but my test sample size so far
is just one over-powered machine.
WARNING: multiple messages have this Message-ID (diff)
From: kbusch@kernel.org (Keith Busch)
Subject: [PATCH] blk-mq: Wait for for hctx requests on CPU unplug
Date: Fri, 5 Apr 2019 16:37:20 -0600 [thread overview]
Message-ID: <20190405223719.GC25081@localhost.localdomain> (raw)
In-Reply-To: <226503cd-53ac-902c-7944-b2748407b1d3@kernel.dk>
On Fri, Apr 05, 2019@04:23:27PM -0600, Jens Axboe wrote:
> On 4/5/19 3:59 PM, Keith Busch wrote:
> > Managed interrupts can not migrate affinity when their CPUs are offline.
> > If the CPU is allowed to shutdown before they're returned, commands
> > dispatched to managed queues won't be able to complete through their
> > irq handlers.
> >
> > Introduce per-hctx reference counting so we can block the CPU dead
> > notification for all allocated requests to complete if an hctx's last
> > CPU is being taken offline.
>
> What does this do to performance? We're doing a map per request...
It should be the same cost as the blk_queue_enter/blk_queue_exit that's
also done per request, which is pretty cheap way to count users. I
don't think I'm measuring a difference, but my test sample size so far
is just one over-powered machine.
next prev parent reply other threads:[~2019-04-05 22:35 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-05 21:59 [PATCH] blk-mq: Wait for for hctx requests on CPU unplug Keith Busch
2019-04-05 21:59 ` Keith Busch
2019-04-05 22:23 ` Jens Axboe
2019-04-05 22:23 ` Jens Axboe
2019-04-05 22:37 ` Keith Busch [this message]
2019-04-05 22:37 ` Keith Busch
2019-04-05 23:04 ` Jens Axboe
2019-04-05 23:04 ` Jens Axboe
2019-04-05 23:36 ` Keith Busch
2019-04-05 23:36 ` Keith Busch
2019-04-06 9:44 ` Dongli Zhang
2019-04-06 9:44 ` Dongli Zhang
2019-04-06 21:27 ` Ming Lei
2019-04-06 21:27 ` Ming Lei
2019-04-07 13:55 ` Dongli Zhang
2019-04-07 13:55 ` Dongli Zhang
2019-04-08 9:49 ` Ming Lei
2019-04-08 9:49 ` Ming Lei
2019-04-08 15:36 ` Keith Busch
2019-04-08 15:36 ` Keith Busch
2019-04-08 15:21 ` Keith Busch
2019-04-08 15:21 ` Keith Busch
2019-04-07 7:51 ` Christoph Hellwig
2019-04-07 7:51 ` Christoph Hellwig
2019-04-08 15:23 ` Keith Busch
2019-04-08 15:23 ` Keith Busch
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