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

Anton Blanchard
2010-01-18T09:57:25Z

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.

Anton