Re: [Patch 6/8] virtual cpu run time

[Shailabh Nagar <nagar@watson.ibm.com>]

Andrew Morton wrote:

> Shailabh Nagar <nagar@watson.ibm.com> wrote:
>  
>
> > delayacct-virtcpu.patch
> >
> > Distinguish between "wall-clock" and "virtual" cpu run times and return
> > both, at per-task and per-tgid granularity.
> >
> > Some architectures adjust tsk->utime+tsk->stime to reflect the time that
> > the kernel wasn't scheduled in hypervised environments and this is the
> > "wall-clock" cpu run time. "Virtual" cpu run time, on the other hand, does
> > not account for the kernel being descheduled.
> >
> > This patch allows the most accurate "virtual" cpu run time, collected by
> > the schedstats code (now shared with delay accounting code), to be returned
> > to user space, in addition to the "wall-clock" cpu time that was being exported
> > earlier. Both these times are useful for workload management in different
> > situations.
> >
> > In a non-virtualized environment, or on architectures which do not adjust
> > tsk->utime/stime, these will effectively be the same value but at different
> > granularities.
> >
> > ...
> >
> > Index: linux-2.6.16/include/linux/taskstats.h
> > ===================================================================
> > --- linux-2.6.16.orig/include/linux/taskstats.h	2006-03-29 18:13:18.000000000 -0500
> > +++ linux-2.6.16/include/linux/taskstats.h	2006-03-29 18:13:20.000000000 -0500
> > @@ -46,8 +46,14 @@ struct taskstats {
> > 	__u64	swapin_count;
> > 	__u64	swapin_delay_total;	/* swapin page fault wait*/
> >
> > -	__u64	cpu_run_total;		/* cpu running time
> > -					 * no count available/provided */
> > +	__u64	cpu_run_real_total;	/* cpu "wall-clock" running time
> > +					 * Potentially accounts for cpu
> > +					 * virtualization, on some arches
> > +					 */
> > +	__u64	cpu_run_virtual_total;	/* cpu "virtual" running time
> > +					 * Uses time intervals as seen by
> > +					 * the kernel
> > +					 */
> > };
> >
> >    
>
> Again, the reader of this struct wants to know what the atomicity rules are.
>  
Will add comment.

>  
>
> > +	d->cpu_run_real_total = (tmp < (nsec_t)d->cpu_run_real_total)? 0: tmp;
> >    
>
> 	lval = expr1 ? expr2 : expr3;
>  
didn't get whats wrong ?

>  
>
> > +	tmp = (nsec_t)d->cpu_run_virtual_total
> > +		+ (nsec_t)jiffies_to_usecs(t3) * 1000;
> >    
>
> umm, Linux doesn't have nsec_t any more.
>
>  
Ok, will switch to s64 everywhere.

--Shailabh


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