Q can be constrained to run on specific cores through the setting of CPU affinity.
Typically, you can set the CPU affinity for the shell you are in, and then processes started within that shell will inherit the affinity.
When NUMA (Non-Uniform Access Memory) is not active, this is achieved through the
taskset command, e.g.
$ taskset -c 0,1,2 q
will run q on cores 0,1 and 2. Or as follows
$ taskset -c 0,1,2 bash
and then all processes started from within that new shell will automatically be restricted to those cores.
Q and NUMA do not work well together. If NUMA is active, you should use
numactl instead of
$ numactl --interleave=all --physcpubind=0,1,2 q
$ echo 0 > /proc/sys/vm/zone_reclaim_mode
You can change
zone_reclaim_mode without restarting q.
You can tell if NUMA is active via the following commands
$ grep NUMA=y /boot/config-`uname -r` CONFIG_NUMA=y CONFIG_AMD_NUMA=y CONFIG_X86_64_ACPI_NUMA=y CONFIG_ACPI_NUMA=y
or testing for the presence of NUMA maps
$ find /proc -name numa_maps /proc/12108/numa_maps /proc/12109/task/12109/numa_maps /proc/12109/numa_maps ...
Other ways to limit resources
On Linux systems, administrators might prefer cgroups as a way of limiting resources.
On Unix systems, memory usage can be constrained using
limits virtual address space to 256MB.
$ ulimit -v 262144
$ psrset -e 2 q
which will run q using processor set 2. Or, to start a shell restricted to those cores:
$ psrset -e 2 bash
Start q.exe with the OS command
start with the
/affinity flag set
C> start /affinity 3 c:\q\w64\q.exe
will run q on core 3.