The BPF extensible scheduler class

Posted Dec 3, 2022 0:23 UTC (Sat) by riking (subscriber, #95706)
Parent article: The BPF extensible scheduler class

The architecture where the kernel can evict the userspace scheduler and go back to CFS is interesting. It's unclear whether a timeout eviction is actually reported to userspace in a way that the system operator can notice?

The BPF extensible scheduler class

Posted Dec 4, 2022 17:46 UTC (Sun) by Manifault (guest, #155796) [Link]

If you look at [0], one of the struct sched_ext_ops callbacks is the following:

/**
* exit - Clean up after the BPF scheduler
* @info: Exit info
*/
void (*exit)(struct scx_exit_info *info);

That ops.exit() callback will be invoked with SCX_EXIT_ERROR_STALL [1] in the event of a hung task causing the BPF scheduler to be evicted, so BPF does have a chance to handle / record / etc the scheduler being evicted for timeouts.

[0]: https://lore.kernel.org/all/20221130082313.3241517-15-tj@...
[1]: https://lore.kernel.org/all/20221130082313.3241517-19-tj@...