From: Christoph Hellwig <hch@lst.de>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: sagi@grimberg.me, linux-nvme@lists.infradead.org,
ming.lei@redhat.com, helgaas@kernel.org,
Keith Busch <kbusch@kernel.org>,
tglx@linutronix.de, Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH 0/4] nvme: Threaded interrupt handling improvements
Date: Tue, 3 Dec 2019 08:42:02 +0100 [thread overview]
Message-ID: <20191203074202.GD23881@lst.de> (raw)
In-Reply-To: <20191202195730.bzzldihtv37odsie@linutronix.de>
On Mon, Dec 02, 2019 at 08:57:30PM +0100, Sebastian Andrzej Siewior wrote:
> > The problem is that by doing the agressive polling we can keep one
> > CPU busy just running the irq handler and starve processes on that
> > CPU if an NVMe queue servers multiple CPUs.
>
> and this is bad? The scheduler will move everything to other CPUs unless
> it is for pinned to this CPU. You can offload even RCU these days :)
> Performance wise it might be better to dedicate one CPU doing this work
> instead spreading it over four CPUs each doing a fraction of it and
> using same cache lines which bounce from one CPU to the next.
Ok, maybe things are getting better these days. I remember we did need
the QUEUE_FLAG_SAME_FORCE flag back in the day to ensure I/O submitters
are properly throttled by the completions they receive.
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prev parent reply other threads:[~2019-12-03 7:42 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-27 17:58 [PATCH 0/4] nvme: Threaded interrupt handling improvements Keith Busch
2019-11-27 17:58 ` [PATCH 1/4] PCI/MSI: Export __pci_msix_desc_mask_irq Keith Busch
2019-11-28 2:42 ` Sagi Grimberg
2019-11-28 3:41 ` Keith Busch
2019-11-28 7:17 ` Christoph Hellwig
2019-11-27 17:58 ` [PATCH 2/4] nvme/pci: Mask legacy and MSI in threaded handler Keith Busch
2019-11-28 3:39 ` Ming Lei
2019-11-28 3:48 ` Keith Busch
2019-11-28 3:58 ` Ming Lei
2019-11-28 4:14 ` Keith Busch
2019-11-28 8:41 ` Ming Lei
2019-11-27 17:58 ` [PATCH 3/4] nvme/pci: Mask MSIx interrupts for threaded handling Keith Busch
2019-11-28 7:19 ` Christoph Hellwig
2019-11-27 17:58 ` [PATCH 4/4] nvme/pci: Spin threaded interrupt completions Keith Busch
2019-11-28 2:46 ` Sagi Grimberg
2019-11-28 3:28 ` Keith Busch
2019-11-28 3:51 ` Ming Lei
2019-11-28 3:58 ` Keith Busch
2019-11-28 7:22 ` Christoph Hellwig
2019-11-29 9:13 ` Sebastian Andrzej Siewior
2019-11-30 18:10 ` Keith Busch
2019-12-02 1:10 ` Ming Lei
2019-12-02 1:30 ` Keith Busch
2019-12-02 16:51 ` Sebastian Andrzej Siewior
2019-11-28 7:50 ` [PATCH 0/4] nvme: Threaded interrupt handling improvements Christoph Hellwig
2019-11-28 17:59 ` Keith Busch
2019-11-29 8:30 ` Christoph Hellwig
2019-11-29 9:46 ` Sebastian Andrzej Siewior
2019-11-29 16:27 ` Keith Busch
2019-11-29 17:05 ` Sebastian Andrzej Siewior
2019-11-30 17:02 ` Keith Busch
2019-12-02 17:05 ` Sebastian Andrzej Siewior
2019-12-02 17:12 ` Christoph Hellwig
2019-12-02 18:06 ` Keith Busch
2019-12-03 7:40 ` Christoph Hellwig
2019-12-02 19:57 ` Sebastian Andrzej Siewior
2019-12-03 7:42 ` Christoph Hellwig [this message]
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