Hi Stephane (and Carl Love and others @ IBM)
We’ve been doing some testing on Power8@Sandia and noticed that none of the
perf qualifiers are valid on Power8 for the internal perf_pmu events and they
don’t work (but are accepted) on the power8_pmu. However, these qualifiers do
work with distros perf and thus something seems to be missing. I’ve pulled the
latest libpfm just to be sure.
First notice the uhk qualifiers are missing from the generic perf events…
pjmucci@white26:~/libpfm4/lib$ LIBPFM_DEBUG=2 ../perf_examples/self cycles:u=1
pfmlib_common.c (pfmlib_init_os.787): OS layer No OS (raw PMU) activated
pfmlib_common.c (pfmlib_init_os.787): OS layer perf_event activated
pfmlib_common.c (pfmlib_init_os.787): OS layer perf_event extended activated
pfmlib_common.c (pfmlib_init_os.790): default OS layer: perf_event
pfmlib_common.c (pfmlib_init_pmus.712): trying POWER4
pfmlib_common.c (pfmlib_init_pmus.712): trying PPC970
pfmlib_common.c (pfmlib_init_pmus.712): trying PPC970MP
pfmlib_common.c (pfmlib_init_pmus.712): trying POWER5
pfmlib_common.c (pfmlib_init_pmus.712): trying POWER5+
pfmlib_common.c (pfmlib_init_pmus.712): trying POWER6
pfmlib_common.c (pfmlib_init_pmus.712): trying POWER7
pfmlib_common.c (pfmlib_init_pmus.712): trying POWER8
pfmlib_common.c (pfmlib_pmu_activate.654): activated POWER8
pfmlib_common.c (pfmlib_init_pmus.712): trying IBM Power Torrent PMU
pfmlib_common.c (pfmlib_init_pmus.712): trying POWERPC_NEST_MCS_RD_BW
pfmlib_common.c (pfmlib_pmu_activate.654): activated POWERPC_NEST_MCS_RD_BW
pfmlib_common.c (pfmlib_init_pmus.712): trying POWERPC_NEST_MCS_WR_BW
pfmlib_common.c (pfmlib_pmu_activate.654): activated POWERPC_NEST_MCS_WR_BW
pfmlib_common.c (pfmlib_init_pmus.712): trying perf_events generic PMU
pfmlib_perf_event_pmu.c (pfm_perf_pmu_supported_plm.133): guessing plm from
power8 PMU plm=0x0
pfmlib_common.c (pfmlib_pmu_activate.654): activated perf_events generic PMU
pfmlib_common.c (pfmlib_init_pmus.712): trying perf_events raw PMU
pfmlib_common.c (pfmlib_pmu_activate.654): activated perf_events raw PMU
pfmlib_common.c (pfmlib_init_pmus.765): 5 PMU detected out of 13 supported
pfmlib_common.c (pfmlib_build_event_pattrs.1114): 0 0 3 2 3 period
pfmlib_common.c (pfmlib_build_event_pattrs.1114): 0 1 3 2 4 freq
pfmlib_common.c (pfmlib_build_event_pattrs.1114): 0 2 3 2 5 precise
pfmlib_common.c (pfmlib_build_event_pattrs.1114): 0 3 2 2 6 excl
pfmlib_common.c (pfmlib_build_event_pattrs.1114): 0 4 2 2 7 mg
pfmlib_common.c (pfmlib_build_event_pattrs.1114): 0 5 2 2 8 mh
pfmlib_common.c (pfmlib_build_event_pattrs.1114): 0 6 3 2 9 cpu
pfmlib_common.c (pfmlib_build_event_pattrs.1114): 0 7 2 2 10 pinned
pfmlib_common.c (pfmlib_parse_event_attr.963): cannot find attribute u
self: event cycles:u=1: invalid event attribute
self: cannot setup events
Ok, no dice. We can see the missing qualifiers. Let’s check if the kernel can
do it...
pjmucci@white26:~/libpfm4/lib$ perf stat -e cycles:u sleep 1
Performance counter stats for 'sleep 1':
372,007 cycles:u
1.002781228 seconds time elapsed
pjmucci@white26:~/libpfm4/lib$ perf stat -e cycles:k sleep 1
Performance counter stats for 'sleep 1':
1,476,676 cycles:k
1.001160681 seconds time elapsed
pjmucci@white26:~/libpfm4/lib$
These look good! So there’s one bug… Now let’s try libpfm’s power8_pmu event,
PMU_CYC:u=1
pjmucci@white26:~/libpfm4/lib$ LIBPFM_DEBUG=2 ../perf_examples/self
PM_RUN_CYC:u=1
<clipped>
pfmlib_common.c (pfmlib_build_event_pattrs.1114): 917 0 2 2 0 u
pfmlib_common.c (pfmlib_build_event_pattrs.1114): 917 1 2 2 1 k
pfmlib_common.c (pfmlib_build_event_pattrs.1114): 917 2 2 2 2 h
pfmlib_common.c (pfmlib_build_event_pattrs.1114): 917 3 3 2 3 period
pfmlib_common.c (pfmlib_build_event_pattrs.1114): 917 4 3 2 4 freq
pfmlib_common.c (pfmlib_build_event_pattrs.1114): 917 5 2 2 6 excl
pfmlib_common.c (pfmlib_build_event_pattrs.1114): 917 6 2 2 7 mg
pfmlib_common.c (pfmlib_build_event_pattrs.1114): 917 7 2 2 8 mh
pfmlib_common.c (pfmlib_build_event_pattrs.1114): 917 8 3 2 9 cpu
pfmlib_common.c (pfmlib_build_event_pattrs.1114): 917 9 2 2 10 pinned
pfmlib_common.c (pfmlib_parse_event.1294): 917 0 0 u
INITIAL: 4,605 PM_RUN_CYC:u=1 (0.00% scaling, raw=4,605,
ena=2,100, run=2,100)
Final counts:
FINAL: 38,666,160,882 PM_RUN_CYC:u=1 (0.00% scaling,
raw=38,666,160,882, ena=9,999,885,066, run=9,999,885,066)
Aha! It took the qualifier… but we don’t know if the number is decent...Lets
try measuring kernel cycles.
pjmucci@white26:~/libpfm4/lib$ LIBPFM_DEBUG=2 ../perf_examples/self
PM_RUN_CYC:u=0:k=1
<clipped>
pfmlib_common.c (pfmlib_parse_event.1294): 917 0 0 u
pfmlib_common.c (pfmlib_parse_event.1294): 917 1 1 k
INITIAL: 4,277 PM_RUN_CYC:u=0:k=1 (0.00% scaling, raw=4,277,
ena=1,876, run=1,876)
Final counts:
FINAL: 38,666,014,163 PM_RUN_CYC:u=0:k=1 (0.00% scaling,
raw=38,666,014,163, ena=9,999,846,334, run=9,999,846,334)
And just for completeness… Just k=1...
pfmlib_common.c (pfmlib_parse_event.1294): 917 0 1 k
INITIAL: 4,922 PM_RUN_CYC:k=1 (0.00% scaling, raw=4,922,
ena=2,218, run=2,218)
Final counts:
FINAL: 38,666,064,958 PM_RUN_CYC:k=1 (0.00% scaling,
raw=38,666,064,958, ena=9,999,862,602, run=9,999,862,602)
So, it seems a few problems.
1) qualifiers for the perf_pmu (ukh) are not supported
2) qualifiers for the power8_pmu (ukh) are supported but not working/being
passed to the kernel
I looked through the code, but it was not intuitive how this all gets handled.
Thoughts?
Thanks
P.S. I can’t figure out how these qualifiers are supposed to work in
check_events, when we always say the OS_encoding is PFM_OS_NONE...
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