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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.
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:
USAGE message:
# ./runqslower -h
usage: [-h] [-p PID | -t TID] [min_us]
Trace high run queue latency
positional arguments:
min_us minimum run queue latecy to trace, in us (default 10000)
optional arguments:
-h, --help show this help message and exit
-p PID, --pid PID trace this PID
-t TID, --tid TID trace this TID only
./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 (thread) 123