meson: Add veristat script

[hodgesds]

Add a meson script to run veristat. This can later be used to generate reports for BPF program complexity at PR time.

local example:

$ meson setup build -Dscheduler=scx_lavd --reconfigure
$ meson compile -C build veristat 
INFO: autodetecting backend as ninja
INFO: calculating backend command to run: /usr/bin/ninja -C /home/hodgesd/scx/build veristat
ninja: Entering directory `/home/hodgesd/scx/build'
[0/1] Running external command veristat (wrapped by meson to set env)
Running veristat on /home/hodgesd/scx/build/scheds/rust/scx_lavd/debug/build/scx_lavd-75563794c6a33502/out/bpf.bpf.o
Processing 'bpf.bpf.o'...
File       Program           Verdict  Duration (us)  Insns  States  Peak states
---------  ----------------  -------  -------------  -----  ------  -----------
bpf.bpf.o  lavd_cpu_offline  success           6666  12566     458          301
bpf.bpf.o  lavd_cpu_online   success           7040  12566     458          301
bpf.bpf.o  lavd_dispatch     success           2349    153      15           15
bpf.bpf.o  lavd_enable       success             46     33       2            2
bpf.bpf.o  lavd_enqueue      success           5614   4499     325          190
bpf.bpf.o  lavd_exit         success             39     25       2            2
bpf.bpf.o  lavd_init         success           6273   8215     375          328
bpf.bpf.o  lavd_init_task    success             57     92       4            4
bpf.bpf.o  lavd_quiescent    success             87     80       6            6
bpf.bpf.o  lavd_runnable     success           6819    112       8            8
bpf.bpf.o  lavd_running      success            721   1416      80           80
bpf.bpf.o  lavd_select_cpu   success           5784    171      17           17
bpf.bpf.o  lavd_stopping     success            137    166      14           14
bpf.bpf.o  lavd_tick         success            272    198      18           18
bpf.bpf.o  lavd_update_idle  success             61     49       3            3
---------  ----------------  -------  -------------  -----  ------  -----------
Done. Processed 1 files, 0 programs. Skipped 15 files, 0 programs.

VNG example:

$ git clone --single-branch -b for-next --depth 1 https://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext.git linux
$ cd linux && vng -v --build --config ../.github/workflows/sched-ext.config
$ make headers && cd ..
$ meson setup build -Dkernel=$(pwd)/linux -Dkernel_headers=./linux/usr/include -Dscheduler=scx_lavd
...
sched_ext schedulers 1.0.2

  User defined options
    kernel        : /home/hodgesd/scx/linux
    kernel_headers: ./linux/usr/include
    scheduler     : scx_lavd

$ meson compile -C build 
$ meson compile -C build veristat  
[    4.605192] virtme-init: waiting for udev to settle
[    4.800171] virtme-init: udev is done
[    4.963616] virtme-init: Setting hostname to virtme-ng...
[    5.018210] ip (556) used greatest stack depth: 12392 bytes left
[    5.156856] virtme-init: starting script
Processing 'bpf.bpf.o'...
File       Program           Verdict  Duration (us)  Insns  States  Peak states
---------  ----------------  -------  -------------  -----  ------  -----------
bpf.bpf.o  lavd_cpu_offline  success           8113  12566     458          299
bpf.bpf.o  lavd_cpu_online   success           8340  12566     458          299
bpf.bpf.o  lavd_dispatch     success           2143    153      15           15
bpf.bpf.o  lavd_enable       success             38     33       2            2
bpf.bpf.o  lavd_enqueue      success           4643   4499     325          190
bpf.bpf.o  lavd_exit         success             31     25       2            2
bpf.bpf.o  lavd_init         success           5466   8215     375          328
bpf.bpf.o  lavd_init_task    success             53     92       4            4
bpf.bpf.o  lavd_quiescent    success             67     80       6            6
bpf.bpf.o  lavd_runnable     success           5728    112       8            8
bpf.bpf.o  lavd_running      success            920   1416      80           80
bpf.bpf.o  lavd_select_cpu   success           4924    171      17           17
bpf.bpf.o  lavd_stopping     success            126    166      14           14
bpf.bpf.o  lavd_tick         success            312    198      18           18
bpf.bpf.o  lavd_update_idle  success             50     49       3            3
---------  ----------------  -------  -------------  -----  ------  -----------
Done. Processed 1 files, 0 programs. Skipped 15 files, 0 programs.
[    6.320858] virtme-init: script returned {0}
Powering off.
[    6.388654] ACPI: PM: Preparing to enter system sleep state S5
[    6.389718] kvm: exiting hardware virtualization
[    6.390623] reboot: Power down

Ideally, when #462 is implemented then the diff version of veristat can run against main to get a report of any BPF program performance changes.

[hodgesds]

Not sure if this is the right approach, but it's the only easy way I could think of getting this to work. My thought is if the github workflow is setup correctly it could use this variable to only build the configured scheduler.

[htejun]

Would it make sense to indicate that it's for running veristat in the option name?

[hodgesds]

Something like veristat-scheduler? I guess if it gets made more generic in the future it can be renamed.