Re: [PATCH] audit: Reduce overhead using a coarse clock

From	Mel Gorman <mgorman@techsingularity.net>
Newsgroups	linux.kernel
Subject	Re: [PATCH] audit: Reduce overhead using a coarse clock
Date	2017-07-04 19:00 +0200
Message-ID	<tZzl7-2yf-3@gated-at.bofh.it> (permalink)
References	<tZuYa-86m-21@gated-at.bofh.it> <tZyS6-2nd-5@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Tue, Jul 04, 2017 at 09:23:55AM -0700, Deepa Dinamani wrote:
> > The patch in question has no explanation as to why a fully-accurate timestamp
> > is required and is likely an oversight.  Using a coarser, but monotically
> > increasing, timestamp the overhead can be eliminated.
> 
> You are right. I was trying to use ktime_get* functions preferably.
> I was aware that current_kernel_time64() could also be used if lesser
> granularity was preferred and that it was faster.
> I forgot to note that in the commit text.
> 

Given the severe overhead (roughly 10% to redis, sysbench-threads), would
you be willing to accept the coarser granularity to avoid audit taking
a major performance hit? I didn't mention it in my own changelog but a
similar 10% hit is also visible in the will-it-scale microbenchmarks that
focus on system calls so it's a fairly broad impact.

-- 
Mel Gorman
SUSE Labs

Thread

[PATCH] audit: Reduce overhead using a coarse clock Mel Gorman <mgorman@techsingularity.net> - 2017-07-04 14:20 +0200
  Re: [PATCH] audit: Reduce overhead using a coarse clock Deepa Dinamani <deepa.kernel@gmail.com> - 2017-07-04 18:30 +0200
    Re: [PATCH] audit: Reduce overhead using a coarse clock Mel Gorman <mgorman@techsingularity.net> - 2017-07-04 19:00 +0200
  Re: [PATCH] audit: Reduce overhead using a coarse clock Arnd Bergmann <arnd@arndb.de> - 2017-07-04 21:30 +0200
    Re: [PATCH] audit: Reduce overhead using a coarse clock Deepa Dinamani <deepa.kernel@gmail.com> - 2017-07-04 21:50 +0200
      Re: [PATCH] audit: Reduce overhead using a coarse clock Paul Moore <paul@paul-moore.com> - 2017-07-06 22:30 +0200
        Re: [PATCH] audit: Reduce overhead using a coarse clock Mel Gorman <mgorman@techsingularity.net> - 2017-07-07 01:40 +0200
        Re: [PATCH] audit: Reduce overhead using a coarse clock Richard Guy Briggs <rgb@redhat.com> - 2017-07-10 16:50 +0200

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