Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
From:   Waiman Long <longman@redhat.com>
To:     Andrew Morton <akpm@linux-foundation.org>,
        Alexey Dobriyan <adobriyan@gmail.com>,
        Luis Chamberlain <mcgrof@kernel.org>,
        Kees Cook <keescook@chromium.org>,
        Jonathan Corbet <corbet@lwn.net>
Cc:     linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
        linux-fsdevel@vger.kernel.org, Davidlohr Bueso <dave@stgolabs.net>,
        Miklos Szeredi <miklos@szeredi.hu>,
        Daniel Colascione <dancol@google.com>,
        Dave Chinner <david@fromorbit.com>,
        Randy Dunlap <rdunlap@infradead.org>,
        Waiman Long <longman@redhat.com>
Subject: [PATCH 0/2] /proc/stat: Reduce irqs counting performance overhead
Date:   Mon,  7 Jan 2019 10:12:56 -0500
Message-Id: <1546873978-27797-1-git-send-email-longman@redhat.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

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