CPU affinity¶
kdb+ 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.
.Q.w
(memory stats)
Basics: Command-line parameter -w
,
System command \w
Linux¶
Use the taskset
command to limit to a certain set of cores, e.g.
taskset -c 0-2,4 q
will run q on cores 0, 1, 2 and 4. Or
taskset -c 0-2,4 bash
and then all processes started from within that new shell will automatically be restricted to those cores.
You can also use numactl -S to specify the cores, perhaps combined with -l to always allocate on the current node or other policies discussed in the linux production notes:
numactl --interleave=all --physcpubind=0,1,2 q
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 ulimit
, e.g.
ulimit -v 262144
limits virtual address space to 256MB.
Solaris¶
Use psrset
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
Windows¶
Start q.exe
with the OS command start
with the /affinity
flag set
start /affinity 3 c:\q\w64\q.exe
will run q on core 0 and 1.