linux-kernel - Re: [PATCH 0/3] lockless sys_times and posix_cpu_clock

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Date:	Wed, 03 Sep 2014 14:38:26 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Andrew Theurer <atheurer@...hat.com>
CC:	linux-kernel@...r.kernel.org, oleg@...hat.com,
	peterz@...radead.org, umgwanakikbuti@...il.com, fweisbec@...il.com,
	akpm@...ux-foundation.org, srao@...hat.com, lwoodman@...hat.com,
	Peter Zijlstra <peterz@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH 0/3] lockless sys_times and posix_cpu_clock_get

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On 08/19/2014 05:21 PM, Andrew Theurer wrote:
> 
>> Thanks to the feedback from Oleg, Peter, Mike, and Frederic, I
>> seem to have a patch series that manages to do times() 
>> locklessly, and apparently correctly.
> 
> 
>> 
>> Oleg points out that the monotonicity alone is not enough of a 
>> guarantee, but that should probably be attacked separately,
>> since that issue is equally present with and without these
>> patches...
>> 
>> The test case below, slightly changed from the one posted by
>> Spencer Candland in 2009, now runs in 11 seconds instead of 5
>> minutes.
>> 
>> Is it worthwhile?  There apparently are some real workloads that
>> call times() a lot, and I believe Sanjay and Andrew have one
>> sitting around.
> 
> Thanks for doing this.  When running a OLTP workload in a KVM VM,
> we saw a 71% increase in performance!  do_sys_times() was a big
> bottleneck for us.

Thanks Andrew, a 71% performance increase seems like it would be
enough to justify merging these patches...


Peter, Ingo, Andrew,

Do any of you have an objection to these patches?

Which tree should I merge them through?

I am happy to resubmit them against any tree, just let
me know where you want the patches to go.

thanks,

Rik
- -- 
All rights reversed
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