Re: [PATCH 4/7] x86/intel_rdt: Implement scheduling support for Intel RDT

[Vikas Shivappa]

On Wed, 6 May 2015, Peter Zijlstra wrote:

> On Mon, May 04, 2015 at 11:39:21AM -0700, Vikas Shivappa wrote:
>
> > > > --- a/arch/x86/include/asm/switch_to.h
> > > > +++ b/arch/x86/include/asm/switch_to.h
> > > > @@ -8,6 +8,9 @@ struct tss_struct;
> > > > void __switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p,
> > > > 		      struct tss_struct *tss);
> > > >
> > > > +#include <asm/intel_rdt.h>
> > > > +#define post_arch_switch(current)	rdt_sched_in(current)
> > > > +
> > > > #ifdef CONFIG_X86_32
> > > >
> > > > #ifdef CONFIG_CC_STACKPROTECTOR
> > >
> > > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> > > > index f9123a8..cacb490 100644
> > > > --- a/kernel/sched/core.c
> > > > +++ b/kernel/sched/core.c
> > > > @@ -2241,6 +2241,7 @@ static struct rq *finish_task_switch(struct task_struct *prev)
> > > > 	prev_state = prev->state;
> > > > 	vtime_task_switch(prev);
> > > > 	finish_arch_switch(prev);
> > > > +	post_arch_switch(current);
> > > > 	perf_event_task_sched_in(prev, current);
> > > > 	finish_lock_switch(rq, prev);
> > > > 	finish_arch_post_lock_switch();
> > >
> > > Not a word in the Changelog on this hook; that's double fail.
> >
> > will add the changelog. we want the current task which no other existing
> > hook provides.
>
> No.
>
> 1) two arch hooks right after one another is FAIL
> 1a) just 'fix' the existing hook
> 2) current is cheap and easily obtainable without passing it as
>    an argument

will fix to just use an existing hook in finish_task_switch and 
current(get_current) since the stack would already be changed ..

Thanks,
Vikas

> 3) why do you need the hook in the first place?
> 3a) why can't you put this in __switch_to()? This is very much x86 only
>     code.
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