Re: [PATCH] perf_counter: Prevent oopses from per-cpu softwarecounters

[Paul Mackerras]

Ingo Molnar writes:

> So how about fixing these sw counts to properly work as percpu counters too? 

OK, so for page faults it looks like I want to look at

	get_cpu_var(vm_event_states).event[PGFAULT]

to get the per-cpu page fault count, as long as
CONFIG_VM_EVENT_COUNTERS is set.

It looks like the scheduler doesn't keep per-cpu counts of context
switches or task migrations, or if it does I couldn't find them.  We
could do stuff in perf_counter_task_sched_in/out to implement per-cpu
context switch and migration counters by adding up the delta values
for each task that gets scheduled onto the cpu.  Or we could add
explicit per-cpu counters for these things in the scheduler.

What do you think?

Paul.
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