Messages in this thread | | | Subject | RE: [PATCH V4] POWER: perf_event: Skip updating kernel counters if register value shrinks | Date | Wed, 27 Apr 2011 14:13:25 +0100 | From | "David Laight" <> |
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> prev and val are both 64 bit variables holding 32 bit numbers, we do not > accumulate in either, they are both replaced by values directly from the > registers. > So prev > val will not always be true.
The code seems to be: prev = local64_read(&event->hw.prev_count); val = read_pmc(event->hw.idx); delta = check_and_compute_delta(prev, val); local64_add(delta, &event->count); Which looks very much like 'prev' being a 64bit counter generated from the 32bit pmc register.
David
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