From: Ming Lei <ming.lei@redhat.com>
To: Bart Van Assche <bvanassche@acm.org>
Cc: Christoph Hellwig <hch@lst.de>,
linux-block@vger.kernel.org, John Garry <john.garry@huawei.com>,
Hannes Reinecke <hare@suse.com>,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: blk-mq: improvement CPU hotplug (simplified version) v3
Date: Mon, 25 May 2020 12:09:52 +0800 [thread overview]
Message-ID: <20200525040952.GB791214@T590> (raw)
In-Reply-To: <26169cd9-49b8-b949-aaa3-9745e821c86c@acm.org>
On Sat, May 23, 2020 at 08:19:58AM -0700, Bart Van Assche wrote:
> On 2020-05-21 19:39, Ming Lei wrote:
> > You may argue that two hw queue may share single managed interrupt, that
> > is possible if driver plays the trick. But if driver plays the trick in
> > this way, it is driver's responsibility to guarantee that the managed
> > irq won't be shutdown if either of the two hctxs are active, such as,
> > making sure that hctx->cpumask + hctx->cpumask <= this managed interrupt's affinity.
> > It is definitely one strange enough case, and this patch doesn't
> > suppose to cover this strange case. But, this patch won't break this
> > case. Also just be curious, do you have such in-tree case? and are you
> > sure the driver uses managed interrupt?
>
> I'm concerned about the block drivers that use RDMA (NVMeOF, SRP, iSER,
> ...). The functions that accept an interrupt vector argument
> (comp_vector), namely ib_alloc_cq() and ib_create_cq(), can be used in
PCI_IRQ_AFFINITY isn't used in RDMA driver, so RDMA NIC uses non-managed
irq.
> such a way that completion interrupts are handled on another CPU than
> those in hctx->cpumask.
As I explained, this patchset doesn't rely on that interrupts have to
be fired on hctx->cpumask, and it only changes the submission io path,
which is blk-mq's generic code path which doesn't depend on any driver's
specific behavior.
Please let us know if your concerns are addressed.
Thanks,
Ming
next prev parent reply other threads:[~2020-05-25 4:10 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-20 17:06 blk-mq: improvement CPU hotplug (simplified version) v3 Christoph Hellwig
2020-05-20 17:06 ` [PATCH 1/6] blk-mq: remove the bio argument to ->prepare_request Christoph Hellwig
2020-05-20 18:16 ` Bart Van Assche
2020-05-22 9:11 ` Hannes Reinecke
2020-05-20 17:06 ` [PATCH 2/6] blk-mq: simplify the blk_mq_get_request calling convention Christoph Hellwig
2020-05-20 18:22 ` Bart Van Assche
2020-05-22 9:13 ` Hannes Reinecke
2020-05-20 17:06 ` [PATCH 3/6] blk-mq: move more request initialization to blk_mq_rq_ctx_init Christoph Hellwig
2020-05-20 20:10 ` Bart Van Assche
2020-05-20 17:06 ` [PATCH 4/6] blk-mq: open code __blk_mq_alloc_request in blk_mq_alloc_request_hctx Christoph Hellwig
2020-05-22 9:17 ` Hannes Reinecke
2020-05-20 17:06 ` [PATCH 5/6] blk-mq: add blk_mq_all_tag_iter Christoph Hellwig
2020-05-20 20:24 ` Bart Van Assche
2020-05-27 6:05 ` Christoph Hellwig
2020-05-22 9:18 ` Hannes Reinecke
2020-05-20 17:06 ` [PATCH 6/6] blk-mq: drain I/O when all CPUs in a hctx are offline Christoph Hellwig
2020-05-22 9:25 ` Hannes Reinecke
2020-05-25 9:20 ` Ming Lei
2020-05-20 21:46 ` blk-mq: improvement CPU hotplug (simplified version) v3 Bart Van Assche
2020-05-21 2:57 ` Ming Lei
2020-05-21 3:50 ` Bart Van Assche
2020-05-21 4:33 ` Ming Lei
2020-05-21 19:15 ` Bart Van Assche
2020-05-22 2:39 ` Ming Lei
2020-05-22 14:47 ` Keith Busch
2020-05-23 3:05 ` Ming Lei
2020-05-23 15:19 ` Bart Van Assche
2020-05-25 4:09 ` Ming Lei [this message]
2020-05-25 15:32 ` Bart Van Assche
2020-05-25 16:38 ` Keith Busch
2020-05-26 0:37 ` Ming Lei
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