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From: Waiman Long <longman@redhat.com>
To: Randy Dunlap <rdunlap@infradead.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Kate Stewart <kstewart@linuxfoundation.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [PATCH] proc/stat: Separate out individual irq counts into /proc/stat_irqs
Date: Thu, 19 Apr 2018 14:44:18 -0400	[thread overview]
Message-ID: <289f924e-3556-0cd9-1b81-8b8f53b7a6e4@redhat.com> (raw)
In-Reply-To: <3b8d1463-a671-add0-9b92-51e7518f1c07@infradead.org>

On 04/19/2018 01:38 PM, Randy Dunlap wrote:
> On 04/19/18 10:09, Waiman Long wrote:
>> It was found that reading /proc/stat could be time consuming on
>> systems with a lot of irqs. For example, reading /proc/stat in a
>> certain 2-socket Skylake server took about 4.6ms because it had over
>> 5k irqs. In that particular case, the majority of the CPU cycles for
>> reading /proc/stat was spent in the kstat_irqs() function.  Therefore,
>> application performance can be impacted if the application reads
>> /proc/stat rather frequently.
>>
>> The "intr" line within /proc/stat contains a sum total of all the irqs
>> that have happened followed by a list of irq counts for each individual
>> irq number. In many cases, the first number is good enough. The
>> individual irq counts may not provide that much more information.
>>
>> In order to avoid this kind of performance issue, all these individual
>> irq counts are now separated into a new /proc/stat_irqs file. The
>> sum total irq count will stay in /proc/stat and be duplicated in
>> /proc/stat_irqs. Applications that need to look up individual irq counts
>> will now have to look into /proc/stat_irqs instead of /proc/stat.
>>
>> Signed-off-by: Waiman Long <longman@redhat.com>
>> ---
>>  fs/proc/stat.c | 48 +++++++++++++++++++++++++++++++++++++++++-------
>>  1 file changed, 41 insertions(+), 7 deletions(-)
> Also please update Documentation/filesystems/proc.txt.
>
> thanks,

Right. I forgot to do that. Will send out v2 to fix that.

-Longman

  reply	other threads:[~2018-04-19 18:44 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-19 17:09 Waiman Long
2018-04-19 17:38 ` Randy Dunlap
2018-04-19 18:44   ` Waiman Long [this message]
2018-04-19 19:43 ` Andrew Morton
2018-04-19 19:57   ` Waiman Long
2018-04-19 20:02   ` Alexey Dobriyan
2018-04-19 19:08 Alexey Dobriyan
2018-04-19 19:28 ` Waiman Long
2018-04-19 19:55   ` Alexey Dobriyan
     [not found]     ` <eb7c1569-e445-5cbb-6d10-2694b625232a@redhat.com>
2018-04-19 20:39       ` Alexey Dobriyan
2018-04-19 20:58         ` Waiman Long
2018-04-19 23:23           ` Joel Fernandes (Google)
2018-04-21 20:34             ` Alexey Dobriyan
2018-04-21 20:36               ` Alexey Dobriyan
2018-04-24  5:54                 ` David Rientjes
2018-04-24  6:18                   ` Alexey Dobriyan
2018-05-02  0:02                     ` Andrew Morton
2018-04-19 21:05         ` Waiman Long

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