Current File : //usr/share/doc/bpfcc-tools/examples/doc/runqslower_example.txt
Demonstrations of runqslower, the Linux eBPF/bcc version.
runqslower shows high latency scheduling times between tasks being
ready to run and them running on CPU after that. For example:
# runqslower
Note: Showing TID (thread id) in the report column. The smallest
execution unit becomes a TID when using the --pid flag as
in that case the tool reports not only the parent pid but
its children threads as well.
Tracing run queue latency higher than 10000 us.
TIME COMM TID LAT(us)
04:16:32 cc1 12924 12739
04:16:32 sh 13640 12118
04:16:32 make 13639 12730
04:16:32 bash 13655 12047
04:16:32 bash 13657 12744
04:16:32 bash 13656 12880
04:16:32 sh 13660 10846
04:16:32 gcc 13663 12681
04:16:32 make 13668 10814
04:16:32 make 13670 12988
04:16:32 gcc 13677 11770
04:16:32 gcc 13678 23519
04:16:32 as 12999 20541
[...]
This shows various processes waiting for available CPU during a Linux kernel
build. By default the output contains delays for more than 10ms.
These delays can be analyzed in depth with "perf sched" tool, see:
* http://www.brendangregg.com/blog/2017-03-16/perf-sched.html
USAGE message:
# ./runqslower -h
usage: runqslower.py [-h] [-p PID | -t TID] [min_us]
Trace high run queue latency
positional arguments:
min_us minimum run queue latency to trace, in us (default 10000)
optional arguments:
-h, --help show this help message and exit
-p PID, --pid PID trace this PID only
-t TID, --tid TID trace this TID only
-P, --previous also show previous task name and TID
examples:
./runqslower # trace run queue latency higher than 10000 us (default)
./runqslower 1000 # trace run queue latency higher than 1000 us
./runqslower -p 123 # trace pid 123
./runqslower -t 123 # trace tid 123 (use for threads only)
./runqslower -P # also show previous task comm and TID
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