From 2b206ee6b0df03a89783c6a9ada363122f918800 Mon Sep 17 00:00:00 2001 From: Sukadev Bhattiprolu Date: Mon, 25 Jan 2016 23:05:36 -0500 Subject: [PATCH] powerpc/perf/hv-24x7: Display change in counter values For 24x7 counters, perf displays the raw value of the 24x7 counter, which is a monotonically increasing value. perf stat -C 0 -e \ 'hv_24x7/HPM_0THRD_NON_IDLE_CCYC__PHYS_CORE,core=1/' \ sleep 1 Performance counter stats for 'CPU(s) 0': 9,105,403,170 hv_24x7/HPM_0THRD_NON_IDLE_CCYC__PHYS_CORE,core=1/ 0.000425751 seconds time elapsed In the typical usage of 'perf stat' this counter value is not as useful as the _change_ in the counter value over the duration of the application. Have h_24x7_event_init() set the event's prev_count to the raw value of the 24x7 counter at the time of initialization. When the application terminates, hv_24x7_event_read() will compute the change in value and report to the perf tool. Similarly, for the transaction interface, clear the event count to 0 at the beginning of the transaction. perf stat -C 0 -e \ 'hv_24x7/HPM_0THRD_NON_IDLE_CCYC__PHYS_CORE,core=1/' \ sleep 1 Performance counter stats for 'CPU(s) 0': 245,758 hv_24x7/HPM_0THRD_NON_IDLE_CCYC__PHYS_CORE,core=1/ 1.006366383 seconds time elapsed Signed-off-by: Sukadev Bhattiprolu Signed-off-by: Michael Ellerman --- arch/powerpc/perf/hv-24x7.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/arch/powerpc/perf/hv-24x7.c b/arch/powerpc/perf/hv-24x7.c index b7a9a03ca59d..77b958f213a0 100644 --- a/arch/powerpc/perf/hv-24x7.c +++ b/arch/powerpc/perf/hv-24x7.c @@ -1222,11 +1222,12 @@ static int h_24x7_event_init(struct perf_event *event) return -EACCES; } - /* see if the event complains */ + /* Get the initial value of the counter for this event */ if (single_24x7_request(event, &ct)) { pr_devel("test hcall failed\n"); return -EIO; } + (void)local64_xchg(&event->hw.prev_count, ct); return 0; } @@ -1289,6 +1290,16 @@ static void h_24x7_event_read(struct perf_event *event) h24x7hw = &get_cpu_var(hv_24x7_hw); h24x7hw->events[i] = event; put_cpu_var(h24x7hw); + /* + * Clear the event count so we can compute the _change_ + * in the 24x7 raw counter value at the end of the txn. + * + * Note that we could alternatively read the 24x7 value + * now and save its value in event->hw.prev_count. But + * that would require issuing a hcall, which would then + * defeat the purpose of using the txn interface. + */ + local64_set(&event->count, 0); } put_cpu_var(hv_24x7_reqb); -- 2.20.1