Re: [PATCH] sched: cpuacct: Use bigger percpu counter batch values for stats counters

Balbir Singh
2010-01-21T15:25:48Z

On Monday 18 January 2010 03:25 PM, Anton Blanchard wrote:
>
> Hi Martin,
>
>> For s390 the jiffies_to_cputime is a compile time constant. No need to
>> initialize it at runtime, no?
>
> Indeed it is, I didn't look closely enough. Same with ia64 so no work to
> do on either arch :)
>
>> The patch itself trades some accuracy (larger cpu accounting value that
>> are stored per-cpu) against runtime overhead (spinlock to transfer the
>> value to the global variable in __percpu_counter_add). Did you
>> calculate how big the loss in accuracy is?
>
> The idea is we are already batching percpu_counter_batch jiffies, so
> with CONFIG_VIRT_CPU_ACCOUNTING we batch the equivalent amount in
> cputime.
>

Hi, Peter, Ingo

Could we please pick up the patch for -tip?

--
Three Cheers,
Balbir Singh