SB-CPU-AFFINITY #

hacking, October 29th 2008

Those wanting control over which CPUs threads run on (and are also lucky enough to be running SBCL on Linux) can give SB-CPU-AFFINITY a try.

Usage: (asdf:oos 'asdf:load-op :sb-cpu-affinity) (use-package :sb-cpu-affinity) (with-cpu-affinity-mask (mask) (print mask)) (with-cpu-affinity-mask (mask :save t) ;; Remove all (clear-cpu-affinity-mask mask) ;; Set CPU 0. (setf (cpu-affinity-p 0 mask) t)) (with-cpu-affinity-mask (mask) (print mask)) (with-cpu-affinity-mask (mask :save t) ;; Only odd CPUs in mask. (dotimes (cpu (cpu-count)) (setf (cpu-affinity-p cpu mask) (oddp cpu)))) (with-cpu-affinity-mask (mask) (print mask))

Caveat: memory malloc'ed for the CPU masks (per call to GET-CPU-AFFINITY-MASK or WITH-CPU-AFFINITY-MASK ) is never released currently, as doing that causes glibc to complain about a double-free, and breaks SBCL. That's a leak of 128 bytes each time — but so long as you only set the affinity mask once per worker thread (and use pooling), it should be a non-issue.

If someone has an insight as to why this is so, and what should be done about it... I'd love to hear.