From: Ming Lei <ming.lei@redhat.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Christoph Hellwig <hch@lst.de>,
Bjorn Helgaas <helgaas@kernel.org>, Jens Axboe <axboe@kernel.dk>,
linux-block@vger.kernel.org, Sagi Grimberg <sagi@grimberg.me>,
linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org,
linux-pci@vger.kernel.org
Subject: Re: [PATCH 4/5] nvme-pci: simplify nvme_setup_irqs() via .setup_affinity callback
Date: Mon, 11 Feb 2019 11:58:11 +0800 [thread overview]
Message-ID: <20190211035810.GB8638@ming.t460p> (raw)
In-Reply-To: <alpine.DEB.2.21.1902101731370.8784@nanos.tec.linutronix.de>
On Sun, Feb 10, 2019 at 05:39:20PM +0100, Thomas Gleixner wrote:
> On Fri, 25 Jan 2019, Ming Lei wrote:
>
> > Use the callback of .setup_affinity() to re-caculate number
> > of queues, and build irqs affinity with help of irq_build_affinity().
> >
> > Then nvme_setup_irqs() gets simplified a lot.
>
> I'm pretty sure you can achieve the same by reworking the core code without
> that callback.
Could you share the idea a bit? As I mentioned, the re-distribution
needs driver's knowledge.
>
> > + /* Fill out vectors at the beginning that don't need affinity */
> > + for (curvec = 0; curvec < affd->pre_vectors; curvec++)
> > + cpumask_copy(&masks[curvec].mask, cpu_possible_mask);
>
> cpu_possible_mask is wrong. Why are you deliberately trying to make this
> special? There is absolutely no reason to do so.
It is just for avoiding to export 'irq_default_affinity'.
>
> These interrupts are not managed and therefore the initial affinity has to
> be irq_default_affinity. Setting them to cpu_possible_mask can and probably
> will evade a well thought out default affinity mask, which was set to
> isolate a set of cores from general purpose interrupts.
>
> This is exactly the thing which happens with driver special stuff and which
> needs to be avoided. There is nothing special about this NVME setup and
> yes, I can see why the current core code is a bit tedious to work with, but
> that does not justify that extra driver magic by any means.
OK, thanks for your explanation.
Thanks,
Ming
next prev parent reply other threads:[~2019-02-11 3:58 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-25 9:53 [PATCH 0/5] genirq/affinity: introduce .setup_affinity to support allocating interrupt sets Ming Lei
2019-01-25 9:53 ` [PATCH 1/5] genirq/affinity: move allocation of 'node_to_cpumask' to irq_build_affinity_masks Ming Lei
2019-02-07 22:02 ` Bjorn Helgaas
2019-01-25 9:53 ` [PATCH 2/5] genirq/affinity: allow driver to setup managed IRQ's affinity Ming Lei
2019-02-07 22:21 ` Bjorn Helgaas
2019-02-10 9:22 ` Ming Lei
2019-02-10 16:30 ` Thomas Gleixner
2019-02-11 3:54 ` Ming Lei
2019-02-11 14:39 ` Bjorn Helgaas
2019-02-11 22:38 ` Thomas Gleixner
2019-02-12 11:17 ` Ming Lei
2019-01-25 9:53 ` [PATCH 3/5] genirq/affinity: introduce irq_build_affinity() Ming Lei
2019-01-25 9:53 ` [PATCH 4/5] nvme-pci: simplify nvme_setup_irqs() via .setup_affinity callback Ming Lei
2019-02-10 16:39 ` Thomas Gleixner
2019-02-11 3:58 ` Ming Lei [this message]
2019-02-10 18:49 ` Thomas Gleixner
2019-02-11 4:09 ` Ming Lei
2019-01-25 9:53 ` [PATCH 5/5] genirq/affinity: remove support for allocating interrupt sets Ming Lei
2019-02-07 22:22 ` Bjorn Helgaas
2019-01-25 9:56 ` [PATCH 0/5] genirq/affinity: introduce .setup_affinity to support " Ming Lei
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