From: Keith Busch <email@example.com> To: Sebastian Andrzej Siewior <firstname.lastname@example.org> Cc: email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org Subject: Re: [RFC PATCH 1/3] nvme/pci: Poll the cq in the primary irq handler Date: Tue, 3 Dec 2019 04:16:26 -0700 [thread overview] Message-ID: <20191203111626.GA86476@C02WT3WMHTD6.lpcnextlight.net> (raw) In-Reply-To: <email@example.com> On Tue, Dec 03, 2019 at 11:09:30AM +0100, Sebastian Andrzej Siewior wrote: > On 2019-12-03 07:22:04 [+0900], Keith Busch wrote: > > The nvme threaded interrupt handler reduces CPU time spent in hard irq > > context, but waking it increases latency for low queue depth workloads. > > > > Poll the completion queue once from the primary handler and wake the > > thread only if more completions remain after. Since there is a window > > of time where the threaded and primary handlers may run simultaneously, > > add a new nvmeq flag so that the two can synchronize which owns processing > > the queue. > > It depends on what you mean by "run simultaneously" but it sounds like > this does not happen. > > The primary handler disables the interrupt source and returns > IRQ_WAKE_THREAD. From now on, the primary handler won't fire (unless it > is a shared handler and someone else gets an interrupt). The driver won't share these interrupts, despite some wierd pci host bridges that force sharing among other devices (ex: see the only user of handle_untracked_irq). That isn't what I was considering though. It's true the controller won't send new MSIs once masked, but my concern is for MSIs on the wire that pass that MMIO mask write. Those retrigger the primary handler after it previously returned IRQ_WAKE_THREAD. _______________________________________________ linux-nvme mailing list firstname.lastname@example.org http://lists.infradead.org/mailman/listinfo/linux-nvme
next prev parent reply other threads:[~2019-12-03 11:16 UTC|newest] Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-12-02 22:22 [RFC PATCH 0/3] nvme threaded interrupt improvements Keith Busch 2019-12-02 22:22 ` [RFC PATCH 1/3] nvme/pci: Poll the cq in the primary irq handler Keith Busch 2019-12-03 7:50 ` Christoph Hellwig 2019-12-03 9:39 ` Sebastian Andrzej Siewior 2019-12-03 11:50 ` Keith Busch 2019-12-03 10:09 ` Sebastian Andrzej Siewior 2019-12-03 11:16 ` Keith Busch [this message] 2019-12-04 10:21 ` Ming Lei 2019-12-02 22:22 ` [RFC PATCH 2/3] nvme/pci: Remove use_threaded_interrupts parameter Keith Busch 2019-12-02 22:22 ` [RFC PATCH 3/3] nvme/pci: Poll for new completions in irq thread Keith Busch 2019-12-03 10:17 ` Sebastian Andrzej Siewior
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --in-reply-to=20191203111626.GA86476@C02WT3WMHTD6.lpcnextlight.net \ --email@example.com \ --firstname.lastname@example.org \ --email@example.com \ --firstname.lastname@example.org \ --email@example.com \ --firstname.lastname@example.org \ --subject='Re: [RFC PATCH 1/3] nvme/pci: Poll the cq in the primary irq handler' \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: link
This is a public inbox, see mirroring instructions for how to clone and mirror all data and code used for this inbox; as well as URLs for NNTP newsgroup(s).