|author||Daniel Bristot de Oliveira <firstname.lastname@example.org>||Wed Oct 21 18:51:33 2020 +0200|
|committer||Daniel Bristot de Oliveira <email@example.com>||Wed Oct 21 18:51:33 2020 +0200|
src/stalld: Increase the sched_debug read buffer if it gets too small Large systems can have impressively large sched_debug files. If the buffer is getting at least close to be filled, double the config_buffer_size variable and re-allocate the memory when appropriate. Signed-off-by: Daniel Bristot de Oliveira <firstname.lastname@example.org>
The stalld program (which stands for ‘stall daemon’) is a mechanism to prevent the starvation of operating system threads in a Linux system. The premise is to start up on a housekeeping cpu (one that is not used for real-application purposes) and to periodically monitor the state of each thread in the system, looking for a thread that has been on a run queue (i.e. ready to run) for a specifed length of time without being run. This condition is usually hit when the thread is on the same cpu as a high-priority cpu-intensive task and therefore is being given no opportunity to run.
When a thread is judged to be starving, stalld changes that thread to use the SCHED_DEADLINE policy and gives the thread a small slice of time for that cpu (specified on the command line). The thread then runs and when that timeslice is used, the thread is then returned to its original scheduling policy and stalld then continues to monitor thread states.
There is now an experimental option to boost using SCHED_FIFO. This logic is used if the running kernel does not support the SCHED_DEADLINE policy and may be forced by using the -F/--force_fifo option.
Usage: stalld [-l] [-v] [-k] [-s] [-f] [-h] [-F] [-c cpu-list] [-p time in ns] [-r time in ns] [-d time in seconds] [-t time in seconds]