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

[Konstantin Khlebnikov]

Peter Zijlstra wrote:
> 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.

Unfortunately, removing task-delay-accounting is not the option =)

> > 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.

I don't think so, this only helps to catch useless declarations and definitions
in code and inside other structures.

> >   #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?

IS_ENABLED(smth) == (defined(smth) || defined(smth_MODULE))
but using it for CONFIG_SCHEDSTATS is overkill, indeed.

> Not much like this stuff.

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