linux-kernel - [PATCH 0/2] /proc/stat: Reduce irqs counting performance overhead

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Date:   Mon,  7 Jan 2019 10:12:56 -0500
From:   Waiman Long <longman@...hat.com>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Jonathan Corbet <corbet@....net>
Cc:     linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, Davidlohr Bueso <dave@...olabs.net>,
        Miklos Szeredi <miklos@...redi.hu>,
        Daniel Colascione <dancol@...gle.com>,
        Dave Chinner <david@...morbit.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Waiman Long <longman@...hat.com>
Subject: [PATCH 0/2] /proc/stat: Reduce irqs counting performance overhead

As newer systems have more and more IRQs and CPUs available in their
system, the performance of reading /proc/stat frequently is getting
worse and worse.

Last year, I had proposed patch to extract out the IRQ line of /proc/stat
into a new procfs file. However, this may break existing applications
that depend on the presence of the IRQ line in /proc/stat.

Davidlohr had proposed a new /proc/stat2 file which is almost the same
as /proc/stat except that it has no IRQ line. This will require change
in applications to use the new procfs file.

This patchset uses a different approach to reduce the performance impact
by using a sysctl parameter to control the maximum frequency at which the
IRQ count computation can be done. The result is that the IRQ counts from
/proc/stat may be a bit stale, but still provide the needed information.

Waiman Long (2):
  /proc/stat: Extract irqs counting code into show_stat_irqs()
  /proc/stat: Add sysctl parameter to control irq counts latency

 Documentation/sysctl/fs.txt | 16 +++++++++
 fs/proc/stat.c              | 87 +++++++++++++++++++++++++++++++++++++++------
 kernel/sysctl.c             | 12 +++++++
 3 files changed, 105 insertions(+), 10 deletions(-)

-- 
1.8.3.1