Use tabs instead of spaces for indentation in process_runqlat.bt. I also
updated comments and fixed a typo.
Signed-off-by: Jose Fernandez <josef@netflix.com>
Add a `scripts` folder to hold scripts that are useful for the project,
and add a bpftrace program to measure the runqueue latency for a process.
bpftrace's built-in runqlat.bt program instruments runqueue latency for
all processes and does not provide a way to filter by PID. For sched_ext
performance work, we are interested in the runqueue latency of a
specific process we are trying to optimize, such as a video game.
Therefore, we need to create a custom bpftrace program to achieve this.
`process_runqlat.bt` instruments runqueue latency for a PID and its
threads. This script measures the runqueue latency for a specified PID
and includes all threads spawned by that process.
USAGE: sudo ./scripts/process_runqlat.bt <PID>
The program output will include:
- Stats by thread (count, avg latency, total latency)
- A histogram of all latency measurements
- Aggregated total stats (count, avg latency, total latency)
Example output when targeting Terraria's main process:
$ sudo ./scripts/process_runqlat.bt 652644
Attaching 5 probes...
Instrumenting runqueue latency for PID 652644. Hit Ctrl-C to end.
@tasks[AsyncActionDisp, 652676]: count 24, average 2, total 67
@tasks[Finalizer, 652646]: count 24, average 6, total 151
@tasks[Main Thread, 652668]: count 1432, average 8, total 12561
@tasks[Terraria.b:gl0, 652672]: count 1421, average 9, total 13120
@tasks[Main Thread, 652667]: count 1037, average 9, total 10091
@tasks[FACT Thread, 652679]: count 1033, average 10, total 11005
@tasks[Terraria:gdrv0, 652671]: count 3511, average 10, total 37047
@tasks[SDLAudioP3, 652678]: count 982, average 10, total 10210
@tasks[Main Thread, 652666]: count 104, average 10, total 1088
@tasks[SDLAudioP2, 652675]: count 982, average 10, total 10461
@tasks[Main Thread, 652644]: count 5840, average 11, total 69177
@tasks[Main Thread, 694917]: count 44, average 14, total 659
@tasks[Terraria.b:cs0, 652650]: count 3288, average 14, total 47300
@tasks[Thread Pool Wor, 695239]: count 1001, average 35, total 35873
@tasks[Thread Pool Wor, 696059]: count 986, average 35, total 34848
@tasks[Thread Pool Wor, 695458]: count 985, average 36, total 35836
@tasks[Thread Pool Wor, 696058]: count 982, average 37, total 36518
@usec_hist:
[0] 16 | |
[1] 360 |@ |
[2, 4) 4650 |@@@@@@@@@@@@@@ |
[4, 8) 14517 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ |
[8, 16) 16593 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@|
[16, 32) 5056 |@@@@@@@@@@@@@@@ |
[32, 64) 6795 |@@@@@@@@@@@@@@@@@@@@@ |
[64, 128) 7106 |@@@@@@@@@@@@@@@@@@@@@@ |
[128, 256) 1926 |@@@@@@ |
[256, 512) 130 | |
[512, 1K) 2 | |
@usec_total_stats: count 57152, average 29, total 1699656
Signed-off-by: Jose Fernandez <josef@netflix.com>
