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

From: Waiman Long
Date: Mon Jan 07 2019 - 10:13:13 EST

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(-)