Messages in this thread | | | Subject | Re: [PATCH] POWER: perf_event: Skip updating kernel counters if register value shrinks | From | Benjamin Herrenschmidt <> | Date | Thu, 07 Apr 2011 14:22:57 +1000 |
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> > Doesn't that mean that power_pmu_read() can only ever increase the value of > > the perf_event and so will essentially -stop- once the counter rolls over ? > > > > Similar comments every where you do this type of comparison. > > > > Cheers, > > Ben. > > Sorry for the nag, but am I missing something about the way the register and > the previous values are reset in the overflow interrupt handler?
Well, not all counters get interrupts right ? Some counters are just free running... I'm not sure when that power_pmu_read() function is actually used by the core, I'm not that familiar with perf, but I'd say better safe than sorry. When comparing counter values, doing in a way that is generally safe vs. wraparounds. Eventually do a helper for that.
Cheers, Ben.
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