linux-scsi.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Bart Van Assche <bvanassche@acm.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>,
	Ming Lei <ming.lei@redhat.com>,
	Keith Busch <keith.busch@intel.com>,
	Hannes Reinecke <hare@suse.com>, Sagi Grimberg <sagi@grimberg.me>,
	linux-scsi@vger.kernel.org, Long Li <longli@microsoft.com>,
	John Garry <john.garry@huawei.com>,
	LKML <linux-kernel@vger.kernel.org>,
	linux-nvme@lists.infradead.org, Jens Axboe <axboe@fb.com>,
	Ingo Molnar <mingo@redhat.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH 1/4] softirq: implement IRQ flood detection mechanism
Date: Wed, 4 Sep 2019 12:47:13 -0700	[thread overview]
Message-ID: <9b924e48-e217-9c11-c1fb-46c92a82ea2d@acm.org> (raw)
In-Reply-To: <20190904180211.GX2332@hirez.programming.kicks-ass.net>

On 9/4/19 11:02 AM, Peter Zijlstra wrote:
> On Wed, Sep 04, 2019 at 10:38:59AM -0700, Bart Van Assche wrote:
>> I think it is widely known that rdtsc is a relatively slow x86 instruction.
>> So I expect that using that instruction will cause a measurable overhead if
>> it is called frequently enough. I'm not aware of any publicly available
>> measurement data however.
> 
> https://www.agner.org/optimize/instruction_tables.pdf
> 
> RDTSC, Ryzen: ~36
> RDTSC, Skylake: ~20
> 
> Sadly those same tables don't list the cost of actual exceptions or even
> IRET :/

Thanks Peter for having looked up these numbers. These numbers are much 
better than last time I checked. Ming, would CONFIG_IRQ_TIME_ACCOUNTING 
help your workload?

Does anyone know which CPUs the following text from 
Documentation/admin-guide/kernel-parameters.txt refers to?

tsc=		[ ... ]
		[x86] noirqtime: Do not use TSC to do irq accounting.
		Used to run time disable IRQ_TIME_ACCOUNTING on any
		platforms where RDTSC is slow and this accounting
		can add overhead.

Bart.

  reply	other threads:[~2019-09-04 19:47 UTC|newest]

Thread overview: 65+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-27  8:53 [PATCH 0/4] genirq/nvme: add IRQF_RESCUE_THREAD for avoiding IRQ flood Ming Lei
2019-08-27  8:53 ` [PATCH 1/4] softirq: implement IRQ flood detection mechanism Ming Lei
2019-08-27 14:42   ` Thomas Gleixner
2019-08-27 16:19     ` Thomas Gleixner
2019-08-27 23:04       ` Ming Lei
2019-08-27 23:12         ` Thomas Gleixner
2019-08-27 22:58     ` Ming Lei
2019-08-27 23:09       ` Thomas Gleixner
2019-08-28 11:06         ` Ming Lei
2019-08-28 11:23           ` Thomas Gleixner
2019-08-28 13:50             ` Ming Lei
2019-08-28 14:07               ` Thomas Gleixner
2019-09-03  3:30                 ` Ming Lei
2019-09-03  5:59                   ` Daniel Lezcano
2019-09-03  6:31                     ` Ming Lei
2019-09-03  6:40                       ` Daniel Lezcano
2019-09-03  7:28                         ` Ming Lei
2019-09-03  7:50                           ` Daniel Lezcano
2019-09-03  9:30                             ` Ming Lei
2019-09-04 17:07                             ` Bart Van Assche
2019-09-04 17:31                               ` Daniel Lezcano
2019-09-04 17:38                                 ` Bart Van Assche
2019-09-04 18:02                                   ` Peter Zijlstra
2019-09-04 19:47                                     ` Bart Van Assche [this message]
2019-09-05  9:11                                       ` Ming Lei
2019-09-05  9:06                                 ` Ming Lei
2019-09-05 10:37                                   ` Daniel Lezcano
2019-09-06  1:22                                     ` Long Li
2019-09-06  4:36                                       ` Daniel Lezcano
2019-09-06  4:44                                         ` Long Li
2019-09-06  1:48                                     ` Ming Lei
2019-09-06  5:14                                       ` Daniel Lezcano
2019-09-06 18:30                                         ` Sagi Grimberg
2019-09-06 18:52                                           ` Keith Busch
2019-09-07  0:01                                           ` Ming Lei
2019-09-10  3:10                                             ` Sagi Grimberg
2019-09-18  0:00                                               ` Long Li
2019-09-20 17:14                                                 ` Sagi Grimberg
2019-09-20 19:12                                                   ` Long Li
2019-09-20 20:45                                                     ` Sagi Grimberg
2019-09-24  0:57                                                       ` Long Li
2019-09-18 14:37                                               ` Ming Lei
2019-09-20 17:09                                                 ` Sagi Grimberg
2019-09-06 14:18                                       ` Keith Busch
2019-09-06 17:50                                         ` Long Li
2019-09-06 22:19                                           ` Ming Lei
2019-09-06 22:25                                             ` Keith Busch
2019-09-06 23:13                                               ` Ming Lei
2019-09-10  0:24                                             ` Ming Lei
2019-09-03  8:09                           ` Thomas Gleixner
2019-09-03  9:24                             ` Ming Lei
2019-08-29  6:15   ` Long Li
2019-08-30  0:55     ` Ming Lei
2019-08-27  8:53 ` [PATCH 2/4] genirq: add IRQF_RESCUE_THREAD Ming Lei
2019-08-27  8:53 ` [PATCH 3/4] nvme: pci: pass IRQF_RESCURE_THREAD to request_threaded_irq Ming Lei
2019-08-27  9:06   ` Johannes Thumshirn
2019-08-27  9:09     ` Ming Lei
2019-08-27  9:12       ` Johannes Thumshirn
2019-08-27 14:34       ` Keith Busch
2019-08-27 14:44         ` Keith Busch
2019-08-27 15:10   ` Bart Van Assche
2019-08-28  1:45     ` Ming Lei
2019-08-27  8:53 ` [PATCH 4/4] genirq: use irq's affinity for threaded irq with IRQF_RESCUE_THREAD Ming Lei
2019-08-27 14:35   ` Keith Busch
2019-09-06  8:50   ` John Garry

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=9b924e48-e217-9c11-c1fb-46c92a82ea2d@acm.org \
    --to=bvanassche@acm.org \
    --cc=axboe@fb.com \
    --cc=daniel.lezcano@linaro.org \
    --cc=hare@suse.com \
    --cc=hch@lst.de \
    --cc=john.garry@huawei.com \
    --cc=keith.busch@intel.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-nvme@lists.infradead.org \
    --cc=linux-scsi@vger.kernel.org \
    --cc=longli@microsoft.com \
    --cc=ming.lei@redhat.com \
    --cc=mingo@redhat.com \
    --cc=peterz@infradead.org \
    --cc=sagi@grimberg.me \
    --cc=tglx@linutronix.de \
    /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
Be sure your reply has a Subject: header at the top and a blank line before the message body.
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).