tools/runqlen.bt: remove 'runnable_weight' field

[AboorvaDevarajan]

In this commit, the 'runnable_weight' field has been removed from the 'cfs_rq' struct in runqlen.bt to align with the current version of Linux, which no longer includes this field.

Reference to the Linux kernel commit (introduced from 5.7-rc1):

torvalds/linux@0dacee1

---

This script always return 0 as runqlen even when the it is actually non-zero.

Force run 4 processes affinitize'd to a single CPU (say, CPU 20) thereby making the runqlen of CPU 20 - 3-4.

Workload:

# taskset -c 20 stress-ng --cpu 4
stress-ng: info:  [68396] defaulting to a 1 day, 0 secs run per stressor
stress-ng: info:  [68396] dispatching hogs: 4 cpu
..
Running

Run the script while the workload is running

Before Patch: (value is always 0)

# ./tools/runqlen.bt 
Attaching 2 probes...
Sampling run queue length at 99 Hertz... Hit Ctrl-C to end.
^C

@runqlen: 
[0, 1)             60129 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@|

After Patch:

 ./tools/runqlen.bt 
Attaching 2 probes...
Sampling run queue length at 99 Hertz... Hit Ctrl-C to end.
^C

@runqlen: 
[0, 1)             57536 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@|
[1, 2)                 2 |                                                    |
[2, 3)                 0 |                                                    |
[3, 4)               454 |                                                    |

Checklist

• Language changes are updated in man/adoc/bpftrace.adoc and if needed in docs/reference_guide.md
• User-visible and non-trivial changes updated in CHANGELOG.md
• The new behaviour is covered by tests