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From: Ming Lei <ming.lei@redhat.com>
To: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Bart Van Assche <bvanassche@acm.org>, Jens Axboe <axboe@fb.com>,
	Hannes Reinecke <hare@suse.com>, Sagi Grimberg <sagi@grimberg.me>,
	linux-scsi@vger.kernel.org, Peter Zijlstra <peterz@infradead.org>,
	Long Li <longli@microsoft.com>,
	John Garry <john.garry@huawei.com>,
	LKML <linux-kernel@vger.kernel.org>,
	linux-nvme@lists.infradead.org,
	Keith Busch <keith.busch@intel.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: Thu, 5 Sep 2019 17:06:19 +0800	[thread overview]
Message-ID: <20190905090617.GB4432@ming.t460p> (raw)
In-Reply-To: <2a8bd278-5384-d82f-c09b-4fce236d2d95@linaro.org>

On Wed, Sep 04, 2019 at 07:31:48PM +0200, Daniel Lezcano wrote:
> Hi,
> 
> On 04/09/2019 19:07, Bart Van Assche wrote:
> > On 9/3/19 12:50 AM, Daniel Lezcano wrote:
> >> On 03/09/2019 09:28, Ming Lei wrote:
> >>> On Tue, Sep 03, 2019 at 08:40:35AM +0200, Daniel Lezcano wrote:
> >>>> It is a scheduler problem then ?
> >>>
> >>> Scheduler can do nothing if the CPU is taken completely by handling
> >>> interrupt & softirq, so seems not a scheduler problem, IMO.
> >>
> >> Why? If there is a irq pressure on one CPU reducing its capacity, the
> >> scheduler will balance the tasks on another CPU, no?
> > 
> > Only if CONFIG_IRQ_TIME_ACCOUNTING has been enabled. However, I don't
> > know any Linux distro that enables that option. That's probably because
> > that option introduces two rdtsc() calls in each interrupt. Given the
> > overhead introduced by this option, I don't think this is the solution
> > Ming is looking for.
> 
> Was this overhead reported somewhere ?

The syscall of gettimeofday() calls ktime_get_real_ts64() which finally
calls tk_clock_read() which calls rdtsc too.

But gettimeofday() is often used in fast path, and block IO_STAT needs to
read it too.

> 
> > See also irqtime_account_irq() in kernel/sched/cputime.c.
> 
> From my POV, this framework could be interesting to detect this situation.

Now we are talking about IRQ_TIME_ACCOUNTING instead of IRQ_TIMINGS, and the
former one could be used to implement the detection. And the only sharing
should be the read of timestamp.

Thanks,
Ming

  parent reply	other threads:[~2019-09-05  9:06 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
2019-09-05  9:11                                       ` Ming Lei
2019-09-05  9:06                                 ` Ming Lei [this message]
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

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