On Wed, 27 Apr 2011, David Laight wrote: > > > 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. >
Which implies that it will only ever be 32 bits wide, just stored in 64.
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