Re: [PATCH] perf/test: Skip leader sampling for s390

[Thomas Richter]

On 3/1/25 01:36, Ian Rogers wrote:
> perf record --count=100000 -e '{cycles,cycles}:Su' -- perf test -w brstack

Ian, Namhyung,

here is my output using this command:
# ./perf record --count=100000 -e '{cycles,cycles}:Su' -- perf test -w brstack
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.106 MB perf.data (1080 samples) ]
# ./perf script
            perf   22194 484835.185113:     100000 cycles:       3ff9e407c8c _dl_map_object_from_fd+0xa3c (/usr/lib/ld64.so.1)
            perf   22194 484835.185114:     100000 cycles:       3ff9e408940 _dl_map_object+0x110 (/usr/lib/ld64.so.1)
            perf   22194 484835.185116:     400000 cycles:       3ff9e40890e _dl_map_object+0xde (/usr/lib/ld64.so.1)
            perf   22194 484835.185117:     900000 cycles:       3ff9e40b572 _dl_name_match_p+0x42 (/usr/lib/ld64.so.1)
            perf   22194 484835.185118:     500000 cycles:       3ff9e407c8c _dl_map_object_from_fd+0xa3c (/usr/lib/ld64.so.1)
            perf   22194 484835.185119:     100000 cycles:       3ff9e40b53e _dl_name_match_p+0xe (/usr/lib/ld64.so.1)
            perf   22194 484835.185120:     100000 cycles:       3ff9e40890e _dl_map_object+0xde (/usr/lib/ld64.so.1)
            perf   22194 484835.185121:     100000 cycles:       3ff9e408904 _dl_map_object+0xd4 (/usr/lib/ld64.so.1)
            perf   22194 484835.185122:     100000 cycles:       3ff9e40369a _dl_map_object_deps+0xbba (/usr/lib/ld64.so.1)
            perf   22194 484835.185123:     100000 cycles:       3ff9e413460 _dl_check_map_versions+0x100 (/usr/lib/ld64.so.1)
            perf   22194 484835.185124:     500000 cycles:       3ff9e40b53e _dl_name_match_p+0xe (/usr/lib/ld64.so.1)
            perf   22194 484835.185125:     100000 cycles:       3ff9e40e7e0 _dl_relocate_object+0x550 (/usr/lib/ld64.so.1)
            perf   22194 484835.185126:     200000 cycles:       3ff9e40e7e0 _dl_relocate_object+0x550 (/usr/lib/ld64.so.1)
            perf   22194 484835.185127:     200000 cycles:       3ff9e409558 check_match+0x18 (/usr/lib/ld64.so.1)
            perf   22194 484835.185128:     200000 cycles:       3ff9e409894 do_lookup_x+0x174 (/usr/lib/ld64.so.1)
            perf   22194 484835.185129:     100000 cycles:       3ff9e409910 do_lookup_x+0x1f0 (/usr/lib/ld64.so.1)
            perf   22194 484835.185130:     100000 cycles:       3ff9e409b1e do_lookup_x+0x3fe (/usr/lib/ld64.so.1)
            perf   22194 484835.185131:     100000 cycles:       3ff9e409894 do_lookup_x+0x174 (/usr/lib/ld64.so.1)
            perf   22194 484835.185132:     100000 cycles:       3ff9e409558 check_match+0x18 (/usr/lib/ld64.so.1)
            perf   22194 484835.187445:     100000 cycles:       3ff9e409ad4 do_lookup_x+0x3b4 (/usr/lib/ld64.so.1)

The difference when using counts instead of frequency is similar. Most of time the numbers are identical, 
but sometime they do not match.

Using task-clock as event, I have similar results. The counts vary a bit, but the numbers are pretty close.
They vary by just a few hundred at the most:

# perf record --count=100000 -e '{task-clock,task-clock}:Su' -- perf test -w brstack
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.016 MB perf.data (246 samples) ]
]# ./perf script
            perf   22223 485235.378380:     402070 task-clock:       3ffbed874c6 _dl_map_object_from_fd+0x276 (/usr/lib/ld64.so.1)
            perf   22223 485235.378380:     404640 task-clock:       3ffbed874c6 _dl_map_object_from_fd+0x276 (/usr/lib/ld64.so.1)
            perf   22223 485235.378779:     399960 task-clock:       3ffbed888de _dl_map_object+0xae (/usr/lib/ld64.so.1)
            perf   22223 485235.378779:     397689 task-clock:       3ffbed888de _dl_map_object+0xae (/usr/lib/ld64.so.1)
            perf   22223 485235.378879:     100055 task-clock:       3ffbed8e7e0 _dl_relocate_object+0x550 (/usr/lib/ld64.so.1)
            perf   22223 485235.378879:     100100 task-clock:       3ffbed8e7e0 _dl_relocate_object+0x550 (/usr/lib/ld64.so.1)
            perf   22223 485235.378979:      99981 task-clock:       3ffbed895ae check_match+0x6e (/usr/lib/ld64.so.1)
            perf   22223 485235.378979:      99876 task-clock:       3ffbed895ae check_match+0x6e (/usr/lib/ld64.so.1)
            perf   22223 485235.379079:      99950 task-clock:       3ffbed8974c do_lookup_x+0x2c (/usr/lib/ld64.so.1)
            perf   22223 485235.379079:      99957 task-clock:       3ffbed8974c do_lookup_x+0x2c (/usr/lib/ld64.so.1)
            perf   22223 485235.379179:     100051 task-clock:       3ffbed8e7f0 _dl_relocate_object+0x560 (/usr/lib/ld64.so.1)
            perf   22223 485235.379179:     100004 task-clock:       3ffbed8e7f0 _dl_relocate_object+0x560 (/usr/lib/ld64.so.1)
            perf   22223 485235.379279:      99933 task-clock:       3ffbed8e7ea _dl_relocate_object+0x55a (/usr/lib/ld64.so.1)
            perf   22223 485235.379279:      99952 task-clock:       3ffbed8e7ea _dl_relocate_object+0x55a (/usr/lib/ld64.so.1)

Thanks for your help
-- 
Thomas Richter, Dept 3303, IBM s390 Linux Development, Boeblingen, Germany
--
IBM Deutschland Research & Development GmbH

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