diff options
| -rw-r--r-- | arch/powerpc/kernel/perf_event.c | 37 |
1 files changed, 30 insertions, 7 deletions
diff --git a/arch/powerpc/kernel/perf_event.c b/arch/powerpc/kernel/perf_event.c index c4063b7..822f630 100644 --- a/arch/powerpc/kernel/perf_event.c +++ b/arch/powerpc/kernel/perf_event.c @@ -398,6 +398,25 @@ static int check_excludes(struct perf_event **ctrs, unsigned int cflags[], return 0; } +static u64 check_and_compute_delta(u64 prev, u64 val) +{ + u64 delta = (val - prev) & 0xfffffffful; + + /* + * POWER7 can roll back counter values, if the new value is smaller + * than the previous value it will cause the delta and the counter to + * have bogus values unless we rolled a counter over. If a coutner is + * rolled back, it will be smaller, but within 256, which is the maximum + * number of events to rollback at once. If we dectect a rollback + * return 0. This can lead to a small lack of precision in the + * counters. + */ + if (prev > val && (prev - val) < 256) + delta = 0; + + return delta; +} + static void power_pmu_read(struct perf_event *event) { s64 val, delta, prev; @@ -416,10 +435,11 @@ static void power_pmu_read(struct perf_event *event) prev = local64_read(&event->hw.prev_count); barrier(); val = read_pmc(event->hw.idx); + delta = check_and_compute_delta(prev, val); + if (!delta) + return; } while (local64_cmpxchg(&event->hw.prev_count, prev, val) != prev); - /* The counters are only 32 bits wide */ - delta = (val - prev) & 0xfffffffful; local64_add(delta, &event->count); local64_sub(delta, &event->hw.period_left); } @@ -449,8 +469,9 @@ static void freeze_limited_counters(struct cpu_hw_events *cpuhw, val = (event->hw.idx == 5) ? pmc5 : pmc6; prev = local64_read(&event->hw.prev_count); event->hw.idx = 0; - delta = (val - prev) & 0xfffffffful; - local64_add(delta, &event->count); + delta = check_and_compute_delta(prev, val); + if (delta) + local64_add(delta, &event->count); } } @@ -458,14 +479,16 @@ static void thaw_limited_counters(struct cpu_hw_events *cpuhw, unsigned long pmc5, unsigned long pmc6) { struct perf_event *event; - u64 val; + u64 val, prev; int i; for (i = 0; i < cpuhw->n_limited; ++i) { event = cpuhw->limited_counter[i]; event->hw.idx = cpuhw->limited_hwidx[i]; val = (event->hw.idx == 5) ? pmc5 : pmc6; - local64_set(&event->hw.prev_count, val); + prev = local64_read(&event->hw.prev_count); + if (check_and_compute_delta(prev, val)) + local64_set(&event->hw.prev_count, val); perf_event_update_userpage(event); } } @@ -1197,7 +1220,7 @@ static void record_and_restart(struct perf_event *event, unsigned long val, /* we don't have to worry about interrupts here */ prev = local64_read(&event->hw.prev_count); - delta = (val - prev) & 0xfffffffful; + delta = check_and_compute_delta(prev, val); local64_add(delta, &event->count); /* |