Discrepancies over Perf and Likwid results for memory bandwidth for a AMD Genoa

[meta]

Hello,

Using LIKWID to collect the number of accesses on a Genoa machine, I am getting pretty accurate numbers for memory read and write accesses; using the events and umask numbers that are used by Likwid,  perf stat -e rXXXX gives me quite different results ().  @thomas   suggested me to use the unit name along with Umask and even number (what we have in sys/devices/amd_df/ . Doing so, I am running this command  perf stat -e amd_df/0x7fe1f/ <app>  , but it gives me 0,

I know this is a perf problem but any thought would be so much appreciated.

                                                                         LIKWID           Perf
DRAM_READS_LOCAL_CHANNEL_0 DFC0 1590857000       0                 r7fe1f
DRAM_READS_LOCAL_CHANNEL_1 DFC1 1590307000    9,854,137,674 r7fe5f
DRAM_READS_LOCAL_CHANNEL_2 DFC2 1590583000     49,125,872,666 r7fe9f
DRAM_READS_LOCAL_CHANNEL_3 DFC3 1590071000     0                   r7fedf
DRAM_READS_LOCAL_CHANNEL_4 DFC4 1590094000   0                 r7fe11f
DRAM_READS_LOCAL_CHANNEL_5 DFC5 1590576000     9,854,761,801 r7fe15f
DRAM_READS_LOCAL_CHANNEL_6 DFC6 1589771000     2,405,455,419 r7fe19f
DRAM_READS_LOCAL_CHANNEL_7 DFC7 1590628000     0                          r7fe1df
DRAM_READS_LOCAL_CHANNEL_8 DFC8 1590263000     0                         r7fe21f
DRAM_READS_LOCAL_CHANNEL_9 DFC9 1590791000     9,857,701,809 r7fe25f
DRAM_READS_LOCAL_CHANNEL_10 DFC10 1590940000      7,448,819,685 r7fe29f
DRAM_READS_LOCAL_CHANNEL_11 DFC11 1590508000      0                          r7fe2df

                                                                     sum 19085389000 88546749054

[Thomas Gruber]

Sorry to say that, but you are using it wrong.....again.

man perf-stat

-e, --event= Select the PMU event. Selection can be:

    - a symbolically formed event like pmu/param1=0x3,param2/ where param1 and param2 are defined as formats for the PMU in /sys/bus/event_source/devices/<pmu>/format/*

    - a symbolically formed event like pmu/config=M,config1=N,config2=K/ where M, N, K are numbers (in decimal, hex, octal format). Acceptable values for each of config, config1 and config2 parameters are defined by corresponding entries in /sys/bus/event_source/devices/<pmu>/format/*

Best,
Thomas

[meta]

Thanks for your help, Thomas,

your suggestions and this (https://github.com/RRZE-HPC/likwid/wiki/TutorialLikwidPerf) helped a lot. I appreciate it.