From: Christoph Hellwig <hch@lst.de>
To: Keith Busch <kbusch@kernel.org>
Cc: sagi@grimberg.me, bigeasy@linutronix.de,
linux-nvme@lists.infradead.org, ming.lei@redhat.com,
helgaas@kernel.org, Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH 0/4] nvme: Threaded interrupt handling improvements
Date: Fri, 29 Nov 2019 09:30:59 +0100 [thread overview]
Message-ID: <20191129083059.GA10032@lst.de> (raw)
In-Reply-To: <20191128175904.GA3011@redsun51.ssa.fujisawa.hgst.com>
On Fri, Nov 29, 2019 at 02:59:04AM +0900, Keith Busch wrote:
> On Thu, Nov 28, 2019 at 08:50:47AM +0100, Christoph Hellwig wrote:
> > + if (to_pci_dev(nvmeq->dev->dev)->msix_enabled)
> > + __pci_msix_desc_mask_irq(irq_get_msi_desc(irq), 1);
> > + else
> > + writel(1 << nvmeq->cq_vector, nvmeq->dev->bar + NVME_REG_INTMS);
>
> Oh, we know which branch this would take before we register the callback,
> so smaller specialized functions don't need if/else checks. I even want
> to remove the shadow doorbell checks for normal devices by giving each
> different submission/completion callbacks too. They are individually
> unmeasurable, but maybe they'll add up! :D
This branch is perfect fodder for the branch predictor. I see aboslutely
no reason to osbfucate the code to get rid of it. We also actually remove
more branches than that by open coding nvme_irq for the threaded irq
case than are added here.
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next prev parent reply other threads:[~2019-11-29 8:31 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 [this message]
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
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