From: Keith Busch <keith.busch@intel.com>
To: Christoph Hellwig <hch@lst.de>
Cc: Joe Korty <joe.korty@ccur.com>,
linux-nvme@lists.infradead.org, linux-block@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/6] genirq: allow assigning affinity to present but not online CPUs
Date: Mon, 6 Feb 2017 12:03:05 -0500 [thread overview]
Message-ID: <20170206170304.GF24601@localhost.localdomain> (raw)
In-Reply-To: <20170205164023.GA9281@lst.de>
On Sun, Feb 05, 2017 at 05:40:23PM +0100, Christoph Hellwig wrote:
> Hi Joe,
>
> On Fri, Feb 03, 2017 at 08:58:09PM -0500, Joe Korty wrote:
> > IIRC, some years ago I ran across a customer system where
> > the #cpus_present was twice as big as #cpus_possible.
> >
> > Hyperthreading was turned off in the BIOS so it was not
> > entirely out of line for the extra cpus to be declared
> > present, even though none of them would ever be available
> > for use.
>
> This sounds like a system we should quirk around instead of optimizing
> for it. Unless I totally misunderstand the idea behind cpu_possible
> and cpu_present.
Can we use the online CPUs and create a new hot-cpu notifier to the nvme
driver to free/reallocate as needed? We were doing that before blk-mq. Now
blk-mq can change the number hardware contexts on a live queue, so we
can reintroduce that behavior to nvme and only allocate what we need.
WARNING: multiple messages have this Message-ID (diff)
From: keith.busch@intel.com (Keith Busch)
Subject: [PATCH 1/6] genirq: allow assigning affinity to present but not online CPUs
Date: Mon, 6 Feb 2017 12:03:05 -0500 [thread overview]
Message-ID: <20170206170304.GF24601@localhost.localdomain> (raw)
In-Reply-To: <20170205164023.GA9281@lst.de>
On Sun, Feb 05, 2017@05:40:23PM +0100, Christoph Hellwig wrote:
> Hi Joe,
>
> On Fri, Feb 03, 2017@08:58:09PM -0500, Joe Korty wrote:
> > IIRC, some years ago I ran across a customer system where
> > the #cpus_present was twice as big as #cpus_possible.
> >
> > Hyperthreading was turned off in the BIOS so it was not
> > entirely out of line for the extra cpus to be declared
> > present, even though none of them would ever be available
> > for use.
>
> This sounds like a system we should quirk around instead of optimizing
> for it. Unless I totally misunderstand the idea behind cpu_possible
> and cpu_present.
Can we use the online CPUs and create a new hot-cpu notifier to the nvme
driver to free/reallocate as needed? We were doing that before blk-mq. Now
blk-mq can change the number hardware contexts on a live queue, so we
can reintroduce that behavior to nvme and only allocate what we need.
next prev parent reply other threads:[~2017-02-06 16:54 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <t6NbP-2IT-5@gated-at.bofh.it>
[not found] ` <t6NbP-2IT-13@gated-at.bofh.it>
[not found] ` <20170204015809.GA16203@zipoli.ccur.kvm>
2017-02-05 16:40 ` [PATCH 1/6] genirq: allow assigning affinity to present but not online CPUs Christoph Hellwig
2017-02-05 16:40 ` Christoph Hellwig
2017-02-06 17:03 ` Keith Busch [this message]
2017-02-06 17:03 ` Keith Busch
2017-02-06 17:03 ` Christoph Hellwig
2017-02-06 17:03 ` Christoph Hellwig
2017-02-03 14:35 spread MSI(-X) vectors to all possible CPUs Christoph Hellwig
2017-02-03 14:35 ` [PATCH 1/6] genirq: allow assigning affinity to present but not online CPUs Christoph Hellwig
2017-02-03 14:35 ` Christoph Hellwig
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