linux-kernel - Re: [PATCH v2] kvm: remove dependence on delay-accounting

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Date:	Mon, 16 Jan 2012 14:33:56 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Konstantin Khlebnikov <khlebnikov@...nvz.org>
Cc:	Ingo Molnar <mingo@...e.hu>, Marcelo Tosatti <mtosatti@...hat.com>,
	Avi Kivity <avi@...hat.com>, linux-kernel@...r.kernel.org,
	kvm@...r.kernel.org
Subject: Re: [PATCH v2] kvm: remove dependence on delay-accounting

On Sat, 2012-01-14 at 20:30 +0400, Konstantin Khlebnikov wrote:
> KVM selects delay-accounting only to get sched-info for steal-time accounting.
> Meanwhile delay-accounting can be disabled by boot option. This is ridiculous.
> 
> This patch adds internal boolean option CONFIG_TASK_SCHED_INFO to enable only
> task->sched_info and its collecting inside scheduler.

Urgh, more stupid config knobs, we should be removing them, not adding
moar.

> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index 868cb83..dd5bf78 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -734,7 +734,6 @@ extern struct user_struct root_user;
>  
>  struct backing_dev_info;
>  
> -#if defined(CONFIG_SCHEDSTATS) || defined(CONFIG_TASK_DELAY_ACCT)
>  struct sched_info {
>  	/* cumulative counters */
>  	unsigned long pcount;	      /* # of times run on this cpu */
> @@ -744,7 +743,6 @@ struct sched_info {
>  	unsigned long long last_arrival,/* when we last ran on a cpu */
>  			   last_queued;	/* when we were last queued to run */
>  };
> -#endif /* defined(CONFIG_SCHEDSTATS) || defined(CONFIG_TASK_DELAY_ACCT) */

Not having that structure helps with compile errors.

>  #ifdef CONFIG_TASK_DELAY_ACCT
>  struct task_delay_info {
> @@ -782,7 +780,7 @@ struct task_delay_info {
>  
>  static inline int sched_info_on(void)
>  {
> -#ifdef CONFIG_SCHEDSTATS
> +#if IS_ENABLED(CONFIG_SCHEDSTATS) || IS_ENABLED(CONFIG_KVM)

WTF is IS_ENABLED and why do you use it?


Not much like this stuff.
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