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From: Christoph Hellwig <hch@lst.de>
To: Ming Lei <ming.lei@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>,
	Thomas Gleixner <tglx@linutronix.de>,
	Jens Axboe <axboe@kernel.dk>, Keith Busch <keith.busch@intel.com>,
	linux-nvme@lists.infradead.org, linux-block@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 7/8] blk-mq: create hctx for each present CPU
Date: Wed, 7 Jun 2017 21:06:59 +0200	[thread overview]
Message-ID: <20170607190659.GA32550@lst.de> (raw)
In-Reply-To: <20170607091038.GA25572@ming.t460p>

On Wed, Jun 07, 2017 at 05:10:46PM +0800, Ming Lei wrote:
> One thing not sure is that we may need to handle new CPU hotplug
> after initialization. Without the CPU hotplug handler, system may
> not scale well when more CPUs are added to sockets.

Adding physical CPUs to sockets is a very rare activity, and we
should not optimize for it.  Taking CPUs that are physically present
offline and online is the case that is interesting, and that's what
this patchset changes.

> Another thing is that I don't see how NVMe handles this situation,
> blk_mq_update_nr_hw_queues() is called in nvme_reset_work(), so
> that means RESET need to be triggered after new CPUs are added to
> system?

Yes.

> I have tried to add new CPUs runtime on Qemu, and not see
> new hw queues are added no matter this patchset is applied or not.

Do you even see the CPUs in your VM?  For physical hotplug you'll
need to reserve spots in the cpumap beforehand.

  reply	other threads:[~2017-06-07 19:06 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-06-03 14:03 spread MSI(-X) vectors to all possible CPUs V2 Christoph Hellwig
2017-06-03 14:03 ` [PATCH 1/8] genirq: allow assigning affinity to present but not online CPUs Christoph Hellwig
2017-06-04 15:14   ` Sagi Grimberg
2017-06-17 23:21   ` Thomas Gleixner
2017-06-03 14:03 ` [PATCH 2/8] genirq: move pending helpers to internal.h Christoph Hellwig
2017-06-04 15:15   ` Sagi Grimberg
2017-06-03 14:03 ` [PATCH 3/8] genirq/affinity: factor out a irq_affinity_set helper Christoph Hellwig
2017-06-04 15:15   ` Sagi Grimberg
2017-06-16 10:23   ` Thomas Gleixner
2017-06-16 11:08   ` Thomas Gleixner
2017-06-16 12:00     ` Thomas Gleixner
2017-06-17 23:14   ` Thomas Gleixner
2017-06-03 14:03 ` [PATCH 4/8] genirq/affinity: assign vectors to all present CPUs Christoph Hellwig
2017-06-04 15:17   ` Sagi Grimberg
2017-06-03 14:04 ` [PATCH 5/8] genirq/affinity: update CPU affinity for CPU hotplug events Christoph Hellwig
2017-06-16 10:26   ` Thomas Gleixner
2017-06-16 10:29   ` Thomas Gleixner
2017-06-03 14:04 ` [PATCH 6/8] blk-mq: include all present CPUs in the default queue mapping Christoph Hellwig
2017-06-04 15:11   ` Sagi Grimberg
2017-06-03 14:04 ` [PATCH 7/8] blk-mq: create hctx for each present CPU Christoph Hellwig
2017-06-04 15:11   ` Sagi Grimberg
2017-06-07  9:10   ` Ming Lei
2017-06-07 19:06     ` Christoph Hellwig [this message]
2017-06-08  2:28       ` Ming Lei
2017-06-07 22:04   ` Omar Sandoval
2017-06-08  6:58     ` Christoph Hellwig
2017-06-03 14:04 ` [PATCH 8/8] nvme: allocate queues for all possible CPUs Christoph Hellwig
2017-06-04 15:13   ` Sagi Grimberg
2017-06-16  6:48 ` spread MSI(-X) vectors to all possible CPUs V2 Christoph Hellwig
2017-06-16  7:28   ` Thomas Gleixner

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