linux-kernel - Re: [PATCH RFC 1/2] kvm: Handle undercommitted guest case in PLE handler

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Message-ID: <507FF87C.2060708@redhat.com>
Date:	Thu, 18 Oct 2012 14:39:24 +0200
From:	Avi Kivity <avi@...hat.com>
To:	Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>
CC:	"Andrew M. Theurer" <habanero@...ux.vnet.ibm.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Rik van Riel <riel@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	Srikar <srikar@...ux.vnet.ibm.com>,
	"Nikunj A. Dadhania" <nikunj@...ux.vnet.ibm.com>,
	KVM <kvm@...r.kernel.org>, Jiannan Ouyang <ouyang@...pitt.edu>,
	chegu vinod <chegu_vinod@...com>,
	LKML <linux-kernel@...r.kernel.org>,
	Srivatsa Vaddagiri <srivatsa.vaddagiri@...il.com>,
	Gleb Natapov <gleb@...hat.com>,
	Andrew Jones <drjones@...hat.com>
Subject: Re: [PATCH RFC 1/2] kvm: Handle undercommitted guest case in PLE
 handler

On 10/09/2012 08:51 PM, Raghavendra K T wrote:
> Here is the summary:
> We do get good benefit by increasing ple window. Though we don't
> see good benefit for kernbench and sysbench, for ebizzy, we get huge
> improvement for 1x scenario. (almost 2/3rd of ple disabled case).
> 
> Let me know if you think we can increase the default ple_window
> itself to 16k.
>

I think so, there is no point running with untuned defaults.

> 
> I can respin the whole series including this default ple_window change.

It can come as a separate patch.

> 
> I also have the perf kvm top result for both ebizzy and kernbench.
> I think they are in expected lines now.
> 
> Improvements
> ================
> 
> 16 core PLE machine with 16 vcpu guest
> 
> base = 3.6.0-rc5 + ple handler optimization patches
> base_pleopt_16k = base + ple_window = 16k
> base_pleopt_32k = base + ple_window = 32k
> base_pleopt_nople = base + ple_gap = 0
> kernbench, hackbench, sysbench (time in sec lower is better)
> ebizzy (rec/sec higher is better)
> 
> % improvements w.r.t base (ple_window = 4k)
> ---------------+---------------+-----------------+-------------------+
>                |base_pleopt_16k| base_pleopt_32k | base_pleopt_nople |
> ---------------+---------------+-----------------+-------------------+
> kernbench_1x   |  0.42371      |  1.15164        |   0.09320         |
> kernbench_2x   | -1.40981      | -17.48282       |  -570.77053       |
> ---------------+---------------+-----------------+-------------------+
> sysbench_1x    | -0.92367      | 0.24241         | -0.27027          |
> sysbench_2x    | -2.22706      |-0.30896         | -1.27573          |
> sysbench_3x    | -0.75509      | 0.09444         | -2.97756          |
> ---------------+---------------+-----------------+-------------------+
> ebizzy_1x      | 54.99976      | 67.29460        |  74.14076         |
> ebizzy_2x      | -8.83386      |-27.38403        | -96.22066         |
> ---------------+---------------+-----------------+-------------------+

So it seems we want dynamic PLE windows.  As soon as we enter overcommit
we need to decrease the window.


-- 
error compiling committee.c: too many arguments to function
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