linux-kernel - Re: [RFC PATCH 0/4] Gang scheduling in CFS

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Date:	Wed, 21 Dec 2011 16:09:36 +0530
From:	Nikunj A Dadhania <nikunj@...ux.vnet.ibm.com>
To:	Ingo Molnar <mingo@...e.hu>, Avi Kivity <avi@...hat.com>
Cc:	peterz@...radead.org, linux-kernel@...r.kernel.org,
	vatsa@...ux.vnet.ibm.com, bharata@...ux.vnet.ibm.com
Subject: Re: [RFC PATCH 0/4] Gang scheduling in CFS

On Mon, 19 Dec 2011 12:23:26 +0100, Ingo Molnar <mingo@...e.hu> wrote:
> 
> * Nikunj A. Dadhania <nikunj@...ux.vnet.ibm.com> wrote:
> 
> So could we please approach this from the benchmarked workload 
> angle first? The highest improvement is in ebizzy:
> 
> >     ebizzy 2vm (improved 15 times, i.e. 1520%)
> 
> What's behind this huge speedup? Does ebizzy use user-space 
> spinlocks perhaps? Could we do something on the user-space side 
> to get a similar speedup?
> 
This is from the perf run on the host:

Baseline:

16.22%         qemu-kvm  [kvm_intel]    [k] free_kvm_area
 8.27%         qemu-kvm  [kvm]          [k] start_apic_timer
 7.53%         qemu-kvm  [kvm]          [k] kvm_put_guest_fpu

Gang:

24.44%         qemu-kvm  [kvm_intel]    [k] free_kvm_area
13.42%         qemu-kvm  [kvm]          [k] start_apic_timer 
 9.91%         qemu-kvm  [kvm]          [k] kvm_put_guest_fpu

Ingo, Avi, I am not getting anything obvious from this. Any ideas?

Regards
Nikunj

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