From: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
To: Michael Ellerman <mpe@ellerman.id.au>
Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Subject: [PATCH 2/2] powerpc/perf/hv-24x7: Display change in counter values
Date: Fri, 29 Jan 2016 19:07:45 -0800 [thread overview]
Message-ID: <20160130030744.GB7330@us.ibm.com> (raw)
In-Reply-To: <20160130030710.GA7330@us.ibm.com>
>From a1aa992fb25fb8e98a5c5724376ae8cc91463de3 Mon Sep 17 00:00:00 2001
From: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Date: Mon, 25 Jan 2016 23:05:36 -0500
Subject: [PATCH 2/2] 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>
---
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 b7a9a03..77b958f 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);
--
2.5.3
next prev parent reply other threads:[~2016-01-30 3:07 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-30 3:07 [PATCH 1/2] powerpc/perf/hv-24x7: Fix usage with chip events Sukadev Bhattiprolu
2016-01-30 3:07 ` Sukadev Bhattiprolu [this message]
2016-02-02 18:17 ` [PATCH 2/2] powerpc/perf/hv-24x7: Display change in counter values Madhavan Srinivasan
2016-02-02 20:23 ` Sukadev Bhattiprolu
2016-03-11 0:30 ` [1/2] powerpc/perf/hv-24x7: Fix usage with chip events Michael Ellerman
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