"Gautham R. Shenoy" <e...@linux.vnet.ibm.com> writes:
> +static inline void snapshot_spurr_idle_entry(void)
> +{
> + *this_cpu_ptr(&idle_entry_spurr_snap) = mfspr(SPRN_SPURR);
> +}
> +
[...]
> +static inline void update_idle_spurr_accounting(void)
> +{
> + u64 *idle_spurr_cycles_ptr = this_cpu_ptr(&idle_spurr_cycles);
> + u64 in_spurr = *this_cpu_ptr(&idle_entry_spurr_snap);
> +
> + *idle_spurr_cycles_ptr += mfspr(SPRN_SPURR) - in_spurr;
> +}
[...]
> +static inline u64 read_this_idle_spurr(void)
> +{
> + /*
> + * If we are reading from an idle context, update the
> + * idle-spurr cycles corresponding to the last idle period.
> + * Since the idle context is not yet over, take a fresh
> + * snapshot of the idle-spurr.
> + */
> + if (get_lppaca()->idle == 1) {
> + update_idle_spurr_accounting();
> + snapshot_spurr_idle_entry();
This samples spurr twice when it could do with just one. I don't know
the performance implications, but will the results be coherent?
