linux-kernel - Re: [PATCH RFC V4 2/3] kvm: Note down when cpu relax intercepted or pause loop exited

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Date:	Mon, 16 Jul 2012 13:01:38 +0300
From:	Avi Kivity <avi@...hat.com>
To:	Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>
CC:	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	Ingo Molnar <mingo@...hat.com>, Rik van Riel <riel@...hat.com>,
	Srikar <srikar@...ux.vnet.ibm.com>,
	S390 <linux-s390@...r.kernel.org>,
	Carsten Otte <cotte@...ibm.com>,
	Christian Borntraeger <borntraeger@...ibm.com>,
	KVM <kvm@...r.kernel.org>, chegu vinod <chegu_vinod@...com>,
	"Andrew M. Theurer" <habanero@...ux.vnet.ibm.com>,
	LKML <linux-kernel@...r.kernel.org>, X86 <x86@...nel.org>,
	Gleb Natapov <gleb@...hat.com>, linux390@...ibm.com,
	Srivatsa Vaddagiri <srivatsa.vaddagiri@...il.com>,
	Joerg Roedel <joerg.roedel@....com>
Subject: Re: [PATCH RFC V4 2/3] kvm: Note down when cpu relax intercepted
 or pause loop exited

On 07/16/2012 11:25 AM, Raghavendra K T wrote:
> From: Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>
> 
> Noting pause loop exited vcpu or cpu relax intercepted helps in
> filtering right candidate to yield. Wrong selection of vcpu;
> i.e., a vcpu that just did a pl-exit or cpu relax intercepted may
> contribute to performance degradation.
> 
> Signed-off-by: Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>
> ---
> V2 was:
> Reviewed-by: Rik van Riel <riel@...hat.com>
> 
>  include/linux/kvm_host.h |   37 +++++++++++++++++++++++++++++++++++++
>  virt/kvm/kvm_main.c      |    5 +++++
>  2 files changed, 42 insertions(+), 0 deletions(-)
> 
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index c446435..fa353bd 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -183,6 +183,18 @@ struct kvm_vcpu {
>  	} async_pf;
>  #endif
>  
> +#ifdef CONFIG_HAVE_KVM_CPU_RELAX_INTERCEPT
> +	/*
> +	 * Cpu relax intercept or pause loop exit optimization
> +	 * cpu_relax_intercepted: set when a vcpu does a pause loop exit
> +	 *  or cpu relax intercepted.
> +	 * dy_eligible: indicates whether vcpu is eligible for directed yield.
> +	 */
> +	struct {
> +		bool cpu_relax_intercepted;
> +		bool dy_eligible;
> +	} ple;

Naming:

- ple is the x86 name, but this is common code.  I'd call it spin_loop.
- cpu_relax_intercepted: can call it in_spin_loop, the original name can
me "are we intercepting cpu_relax or not" which may be useful at one
point (when we know we aren't overcommitted)
- dy_eligible: I'd like to understand the algorithm more and would want
the name to reflect it, will come to this later if I have a better idea.

> +#endif

blank line.

>  	struct kvm_vcpu_arch arch;
>  };
>  


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


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