Messages in this thread | | | Date | Mon, 13 Oct 2008 12:15:29 +0200 (CEST) | From | Oliver Weihe <> | Subject | NUMA allocator on Opteron systems does non-local allocation on node0 |
| |
Hi Andi,
I'm not sure if you're the right person for this but I hope you are!
I've notived that the memory allocation on NUMA systems (Opterons) does memory allocation on non-local nodes for processes running node0 even if local memory is available. (Kernel 2.6.25 and above)
Currently I'm playing around with a quadsocket quadcore Opteron but I've observed this behavior on other Opteron systems aswell.
Hardware specs: 1x Supermicro H8QM3-2 4x Quadcore Opteron 16x 2GiB (8 GiB memory per node)
OS: currently openSUSE 10.3 but I've observed this on other distros aswell Kernel: 2.6.22.* (openSUSE) / 2.6.25.4 / 2.6.25.5 / 2.6.27 (vanilla config)
Steps to reproduce: Start an application which needs alot of memory and watch the memory usage per node (I'm using "watch -n 1 numastat --hardware" to watch the memory usage per node) A quick&dirty code which allocates a big array and writes data into the array is enough!
In my setup I'm allocating an array of ~7GiB memory size in a singlethreaded application. Startup: numactl --cpunodebind=X ./app For X=1,2,3 it works as expected, all memory is allocated on the local node. For X=0 I can see the memory beeing allocated on node0 as long as ~3GiB are "free" on node0. At this point the kernel starts using memory from node1 for the app!
For parallel realworld apps I've seen a performance penalty of 30% compared to older kernels!
numactl --cpunodebind=0 --membind=0 ./app "solves" the problem in this case but thats not the point!
--
Regards, Oliver Weihe
| |