State of hardware performance monitoring in WSL2

[christian-vorhemus]

I read mixed signals [1] [2] to which extent we can access the Performance Monitoring Unit by using the perf command. I cloned and compiled the perf tool present in https://github.com/microsoft/WSL2-Linux-Kernel and when I run sudo ./perf stat -d ls I get the following output:

 Performance counter stats for 'ls':

              1.76 msec task-clock                #    0.730 CPUs utilized
                 0      context-switches          #    0.000 K/sec
                 0      cpu-migrations            #    0.000 K/sec
               108      page-faults               #    0.061 M/sec
   <not supported>      cycles
   <not supported>      instructions
   <not supported>      branches
   <not supported>      branch-misses
   <not supported>      L1-dcache-loads
   <not supported>      L1-dcache-load-misses
   <not supported>      LLC-loads
   <not supported>      LLC-load-misses

       0.002411486 seconds time elapsed

       0.002558000 seconds user
       0.000000000 seconds sys

Especially getting the cache misses would be interesting for my use case. Is it expected that measures like cycles, LLC-loads are "not supported" in WSL2 or did I do something wrong? If the former, is support for it planned?

[1] https://stackoverflow.com/questions/60237123/is-there-any-method-to-run-perf-under-wsl#comment125398632_60276918
[2] #329 (comment)

[benhillis]

Yeah we have a backlog item to add additional perf counters, but unfortunately there isn't a great API to query if the host supports them. It's something we're looking into.

[AndyAyersMS]

@benhillis any update on this?

[mingshi2333]

@benhillis any update on this?

the lastest kernel's condition works like this, but still not support llc, It need more work to finish it

[oscarbg]

+1 on LLC metrics..

getting on Zen4:

             7209      branch-misses:u                  #    6.49% of all branches
     <not counted>      L1-dcache-loads:u                                                       (0.00%)
     <not counted>      L1-dcache-load-misses:u                                                 (0.00%)
   <not supported>      LLC-loads:u
   <not supported>      LLC-load-misses:u

[kh-abd-kh]

I used this
sudo apt install linux-tools-generic

/usr/lib/linux-tools/5.15.0-112-generic/perf stat ls
............
..........
.............

Performance counter stats for 'ls':

          2.11 msec task-clock:u              #    0.762 CPUs utilized
             0      context-switches:u        #    0.000 /sec
             0      cpu-migrations:u          #    0.000 /sec
           117      page-faults:u             #   55.508 K/sec
       1660148      cycles:u                  #    0.788 GHz
        123771      stalled-cycles-frontend:u #    7.46% frontend cycles idle
        389595      stalled-cycles-backend:u  #   23.47% backend cycles idle
       1856800      instructions:u            #    1.12  insn per cycle
                                              #    0.21  stalled cycles per insn
        400912      branches:u                #  190.204 M/sec
         15016      branch-misses:u           #    3.75% of all branches

   0.002766014 seconds time elapsed

   0.000285000 seconds user
   0.000000000 seconds sys

I hope this might help

[elazarg]

$ /usr/lib/linux-tools/6.8.0-45-generic/perf stat ls
event syntax error: 'cpu_core/TOPDOWN.SLOTS,metric-id=cpu_core!3TOPDOWN.SLOTS!3/,cpu_core/topdown-retiring,metric-id=cpu_core!3topdo..'
                     \___ Bad event or PMU

Unable to find PMU or event on a PMU of 'cpu_core'

Initial error:
event syntax error: 'cpu_core/TOPDOWN.SLOTS,metric-id=cpu_core!3TOPDOWN.SLOTS!3/,cpu_core/topdown-retiring,metric-id=cpu_core!3topdo..'
                     \___ Cannot find PMU `cpu_core'. Missing kernel support?
...

 Performance counter stats for 'ls':

              1.69 msec task-clock:u                     #    0.235 CPUs utilized
                 0      context-switches:u               #    0.000 /sec
                 0      cpu-migrations:u                 #    0.000 /sec
                99      page-faults:u                    #   58.708 K/sec
   <not supported>      cycles:u
   <not supported>      instructions:u
   <not supported>      branches:u
   <not supported>      branch-misses:u

       0.007168466 seconds time elapsed

       0.002439000 seconds user
       0.000000000 seconds sys

[Spear-Neil]

@benhillis any update on this?

the lastest kernel's condition works like this, but still not support llc, It need more work to finish it

Did you use a user customized kernel or microsoft-standard-WSL2? my kernel version is 5.15.167.4-microsoft-standard-WSL2

[remondma]

Any update?
I also got the same result as @elazarg with the latest WSL2 and 6.8.0-60-generic/perf