Messages in this thread | | | Subject | Re: [PATCH v7 1/5] powerpc/perf/hv-24x7: Fix inconsistent output values incase multiple hv-24x7 events run | From | Madhavan Srinivasan <> | Date | Wed, 29 Apr 2020 14:26:06 +0530 |
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On 3/27/20 12:06 PM, Kajol Jain wrote: > Commit 2b206ee6b0df ("powerpc/perf/hv-24x7: Display change in counter > values")' added to print _change_ in the counter value rather then raw > value for 24x7 counters. Incase of transactions, the event count > is set to 0 at the beginning of the transaction. It also sets > the event's prev_count to the raw value at the time of initialization. > Because of setting event count to 0, we are seeing some weird behaviour, > whenever we run multiple 24x7 events at a time. > > For example: > > command#: ./perf stat -e "{hv_24x7/PM_MCS01_128B_RD_DISP_PORT01,chip=0/, > hv_24x7/PM_MCS01_128B_RD_DISP_PORT01,chip=1/}" > -C 0 -I 1000 sleep 100 > > 1.000121704 120 hv_24x7/PM_MCS01_128B_RD_DISP_PORT01,chip=0/ > 1.000121704 5 hv_24x7/PM_MCS01_128B_RD_DISP_PORT01,chip=1/ > 2.000357733 8 hv_24x7/PM_MCS01_128B_RD_DISP_PORT01,chip=0/ > 2.000357733 10 hv_24x7/PM_MCS01_128B_RD_DISP_PORT01,chip=1/ > 3.000495215 18,446,744,073,709,551,616 hv_24x7/PM_MCS01_128B_RD_DISP_PORT01,chip=0/ > 3.000495215 18,446,744,073,709,551,616 hv_24x7/PM_MCS01_128B_RD_DISP_PORT01,chip=1/ > 4.000641884 56 hv_24x7/PM_MCS01_128B_RD_DISP_PORT01,chip=0/ > 4.000641884 18,446,744,073,709,551,616 hv_24x7/PM_MCS01_128B_RD_DISP_PORT01,chip=1/ > 5.000791887 18,446,744,073,709,551,616 hv_24x7/PM_MCS01_128B_RD_DISP_PORT01,chip=0/ > > Getting these large values in case we do -I. > > As we are setting event_count to 0, for interval case, overall event_count is not > coming in incremental order. As we may can get new delta lesser then previous count. > Because of which when we print intervals, we are getting negative value which create > these large values. > > This patch removes part where we set event_count to 0 in function > 'h_24x7_event_read'. There won't be much impact as we do set event->hw.prev_count > to the raw value at the time of initialization to print change value. > > With this patch > In power9 platform > > command#: ./perf stat -e "{hv_24x7/PM_MCS01_128B_RD_DISP_PORT01,chip=0/, > hv_24x7/PM_MCS01_128B_RD_DISP_PORT01,chip=1/}" > -C 0 -I 1000 sleep 100 > > 1.000117685 93 hv_24x7/PM_MCS01_128B_RD_DISP_PORT01,chip=0/ > 1.000117685 1 hv_24x7/PM_MCS01_128B_RD_DISP_PORT01,chip=1/ > 2.000349331 98 hv_24x7/PM_MCS01_128B_RD_DISP_PORT01,chip=0/ > 2.000349331 2 hv_24x7/PM_MCS01_128B_RD_DISP_PORT01,chip=1/ > 3.000495900 131 hv_24x7/PM_MCS01_128B_RD_DISP_PORT01,chip=0/ > 3.000495900 4 hv_24x7/PM_MCS01_128B_RD_DISP_PORT01,chip=1/ > 4.000645920 204 hv_24x7/PM_MCS01_128B_RD_DISP_PORT01,chip=0/ > 4.000645920 61 hv_24x7/PM_MCS01_128B_RD_DISP_PORT01,chip=1/ > 4.284169997 22 hv_24x7/PM_MCS01_128B_RD_DISP_PORT01,chip=0/ > > Signed-off-by: Kajol Jain <kjain@linux.ibm.com> > Suggested-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Tested-by: Madhavan Srinivasan <maddy@linux.ibm.com>
> --- > arch/powerpc/perf/hv-24x7.c | 10 ---------- > 1 file changed, 10 deletions(-) > > diff --git a/arch/powerpc/perf/hv-24x7.c b/arch/powerpc/perf/hv-24x7.c > index 573e0b309c0c..48e8f4b17b91 100644 > --- a/arch/powerpc/perf/hv-24x7.c > +++ b/arch/powerpc/perf/hv-24x7.c > @@ -1400,16 +1400,6 @@ 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);
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