55 lines
2.4 KiB
Markdown
55 lines
2.4 KiB
Markdown
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# stalld
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The stalld program (which stands for 'stall daemon') is a
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mechanism to prevent the *starvation* of operating system threads in a
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Linux system. The premise is to start up on a *housekeeping* cpu (one
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that is not used for real-application purposes) and to periodically
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monitor the state of each thread in the system, looking for a thread
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that has been on a run queue (i.e. ready to run) for a specifed length
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of time without being run. This condition is usually hit when the
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thread is on the same cpu as a high-priority cpu-intensive task and
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therefore is being given no opportunity to run.
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When a thread is judged to be starving, stalld changes
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that thread to use the SCHED_DEADLINE policy and gives the thread a
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small slice of time for that cpu (specified on the command line). The
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thread then runs and when that timeslice is used, the thread is then
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returned to its original scheduling policy and stalld then
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continues to monitor thread states.
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There is now an experimental option to boost using SCHED_FIFO. This
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logic is used if the running kernel does not support the
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SCHED_DEADLINE policy and may be forced by using the -F/--force_fifo
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option.
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## Command Line Options
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`Usage: stalld [-l] [-v] [-k] [-s] [-f] [-h] [-F]
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[-c cpu-list]
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[-p time in ns] [-r time in ns]
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[-d time in seconds] [-t time in seconds]`
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### Logging options
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- -l/--log_only: only log information (do not boost) [false]
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- -v/--verbose: print info to the std output [false]
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- -k/--log_kmsg: print log to the kernel buffer [false]
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- -s/--log_syslog: print log to syslog [true]
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### Startup options
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- -c/--cpu: list of cpus to monitor for stalled threads [all cpus]
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- -f/--foreground: run in foreground [false but true when -v]
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- -P/--pidfile: write daemon pid to specified file [no pidfile]
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### Boosting options
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- -p/--boost_period: SCHED_DEADLINE period [ns] that the starving task will receive [1000000000]
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- -r/--boost_runtime: SCHED_DEADLINE runtime [ns] that the starving task will receive [20000]
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- -d/--boost_duration: how long [s] the starving task will run with SCHED_DEADLINE [3]
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- -F/--force_fifo: force using SCHED_FIFO for boosting
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### Monitoring options
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- -t/--starving_threshold: how long [s] the starving task will wait before being boosted [60]
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- -A/--aggressive_mode: dispatch one thread per run queue, even when there is no starving
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threads on all CPU (uses more CPU/power). [false]
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### Miscellaneous
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- -h/--help: print this menu
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