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

From: Nikunj A Dadhania
Date: Wed Dec 21 2011 - 05:38:27 EST


On Mon, 19 Dec 2011 12:23:26 +0100, Ingo Molnar <mingo@xxxxxxx> wrote:
>
> * Nikunj A. Dadhania <nikunj@xxxxxxxxxxxxxxxxxx> 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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