diff options
| author | James Hogan <james.hogan@imgtec.com> | 2013-02-27 16:16:38 +0000 |
|---|---|---|
| committer | James Hogan <james.hogan@imgtec.com> | 2013-03-15 13:20:03 +0000 |
| commit | c6ac1e6edacc7e1fb0405d61f95a797c6a712411 (patch) | |
| tree | 8794cd7bbb6873aaf5cafdaa75af0daf35409dfa /arch/metag | |
| parent | db59932f62386cdfd8510c27a83118c5e915e9ea (diff) | |
metag: perf: add missing prev_count updates
The prev_count needs setting when changing the counter value, otherwise
the calculated delta will be wrong, which for frequency sampling
(dynamic period sampling) results in sampling at too high a frequency.
For non-interrupting performance counters it should also be cleared when
enabling the counter since the write to the PERF_COUNT register will
clear the perf counter.
This also includes a minor change to remove the u64 cast from the
metag_pmu->write() call as metag_pmu->write() takes a u32 anyway, and in
any case GCC is smart enough to optimise away the cast.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Diffstat (limited to 'arch/metag')
| -rw-r--r-- | arch/metag/kernel/perf/perf_event.c | 12 |
1 files changed, 10 insertions, 2 deletions
diff --git a/arch/metag/kernel/perf/perf_event.c b/arch/metag/kernel/perf/perf_event.c index a00f527eade..5bf984feaaa 100644 --- a/arch/metag/kernel/perf/perf_event.c +++ b/arch/metag/kernel/perf/perf_event.c @@ -240,8 +240,10 @@ int metag_pmu_event_set_period(struct perf_event *event, if (left > (s64)metag_pmu->max_period) left = metag_pmu->max_period; - if (metag_pmu->write) - metag_pmu->write(idx, (u64)(-left) & MAX_PERIOD); + if (metag_pmu->write) { + local64_set(&hwc->prev_count, -(s32)left); + metag_pmu->write(idx, -left & MAX_PERIOD); + } perf_event_update_userpage(event); @@ -651,6 +653,12 @@ static void metag_pmu_enable_counter(struct hw_perf_event *event, int idx) * set to a specific value that needs preserving. */ tmp |= metag_in32(PERF_COUNT(idx)) & 0x00ffffff; + else + /* + * Older cores reset the counter on write, so prev_count needs + * resetting too so we can calculate a correct delta. + */ + local64_set(&event->prev_count, 0); metag_out32(tmp, PERF_COUNT(idx)); unlock: |