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author | Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com> | 2016-01-26 07:05:36 +0300 |
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committer | Michael Ellerman <mpe@ellerman.id.au> | 2016-03-10 14:56:55 +0300 |
commit | 2b206ee6b0df03a89783c6a9ada363122f918800 (patch) | |
tree | d31a1dca3ba011bbef8e3ddda9412d7e749bf4fe /arch/powerpc/perf/hv-24x7.c | |
parent | e5a5886d7ae32b7afebfffecca340e466e4be2d1 (diff) | |
download | linux-2b206ee6b0df03a89783c6a9ada363122f918800.tar.xz |
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 <sukadev@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Diffstat (limited to 'arch/powerpc/perf/hv-24x7.c')
-rw-r--r-- | arch/powerpc/perf/hv-24x7.c | 13 |
1 files changed, 12 insertions, 1 deletions
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); |