UNB/ CS/ David Bremner/ blog/ posts/ Baby steps towards schroot and slurm cooperation.

Unfortunately schroot does not maintain CPU affinity 1. This means in particular that parallel builds have the tendency to take over an entire slurm managed server, which is kindof rude. I haven't had time to automate this yet, but following demonstrates a simple workaround for interactive building.

╭─ simplex:~
╰─% schroot --preserve-environment -r -c polymake
(unstable-amd64-sbuild)bremner@simplex:~$ echo $SLURM_CPU_BIND_LIST
(unstable-amd64-sbuild)bremner@simplex:~$ grep Cpus /proc/self/status
Cpus_allowed:   ffff,ffffffff,ffffffff
Cpus_allowed_list:      0-79
(unstable-amd64-sbuild)bremner@simplex:~$ taskset $SLURM_CPU_BIND_LIST bash
(unstable-amd64-sbuild)bremner@simplex:~$ grep Cpus /proc/self/status
Cpus_allowed:   5555,55555555,55555555
Cpus_allowed_list:      0,2,4,6,8,10,12,14,16,18,20,22,24,26,28,30,32,34,36,38,40,42,44,46,48,50,52,54,56,58,60,62,64,66,68,70,72,74,76,78

Next steps

In principle the schroot configuration parameter can be used to run taskset before every command. In practice it's a bit fiddly because you need a shell script shim (because the environment variable) and you need to e.g. goof around with bind mounts to make sure that your script is available in the chroot. And then there's combining with ccache and eatmydata...