use SCHED_BATCH scheduling priority for indexing threads #537
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This uses
sched_setscheduler(2)to set the LinuxSCHED_BATCHpolicy for indexing threads. This will only work on Linux, on other Posix platforms the implementation ofsetBatchPriority()will be guarded out by an ifdef (arguably on other Posix systems you could set a nice value as an alternative to usingSCHED_BATCH).There's a good overview of this feature in sched(7) and some benchmarks comparing it to nice values here. Note that the scheduling policy is a separate concept than nice values, so users can still renice ccls processes.
The motivation for this change is to make ccls work a bit better on my workstation when I'm using other interactive programs (emacs itself, firefox, etc.) but also indexing a large amount of code.