I need some help to determine whether the memory bandwidth I'm seeing under Linux on my server is normal or not. Here's the server spec: HP ProLiant DL165 G7 2x AMD Opteron 6164 HE 12-Core 40 GB RAM (10 x 4GB DDR1333) Debian 6.0 Using mbw on this server I get the following numbers: foo1:~# mbw -n 3 1024 Long uses 8 bytes. Allocating 2*134217728 elements = 2147483648 bytes of memory. Using 262144 bytes as blocks for memcpy block copy test. Getting down to business... Doing 3 runs per test. 0 Method: MEMCPY Elapsed: 0.58047 MiB: 1024.00000 Copy: 1764.082 MiB/s 1 Method: MEMCPY Elapsed: 0.58012 MiB: 1024.00000 Copy: 1765.152 MiB/s 2 Method: MEMCPY Elapsed: 0.58010 MiB: 1024.00000 Copy: 1765.201 MiB/s AVG Method: MEMCPY Elapsed: 0.58023 MiB: 1024.00000 Copy: 1764.811 MiB/s 0 Method: DUMB Elapsed: 0.36174 MiB: 1024.00000 Copy: 2830.778 MiB/s 1 Method: DUMB Elapsed: 0.35869 MiB: 1024.00000 Copy: 2854.817 MiB/s 2 Method: DUMB Elapsed: 0.35848 MiB: 1024.00000 Copy: 2856.481 MiB/s AVG Method: DUMB Elapsed: 0.35964 MiB: 1024.00000 Copy: 2847.310 MiB/s 0 Method: MCBLOCK Elapsed: 0.23546 MiB: 1024.00000 Copy: 4348.860 MiB/s 1 Method: MCBLOCK Elapsed: 0.23544 MiB: 1024.00000 Copy: 4349.230 MiB/s 2 Method: MCBLOCK Elapsed: 0.23544 MiB: 1024.00000 Copy: 4349.359 MiB/s AVG Method: MCBLOCK Elapsed: 0.23545 MiB: 1024.00000 Copy: 4349.149 MiB/s On one of my other servers (based on Intel Xeon E3-1270): foo2:~# mbw -n 3 1024 Long uses 8 bytes. Allocating 2*134217728 elements = 2147483648 bytes of memory. Using 262144 bytes as blocks for memcpy block copy test. Getting down to business... Doing 3 runs per test. 0 Method: MEMCPY Elapsed: 0.18960 MiB: 1024.00000 Copy: 5400.901 MiB/s 1 Method: MEMCPY Elapsed: 0.18922 MiB: 1024.00000 Copy: 5411.690 MiB/s 2 Method: MEMCPY Elapsed: 0.18944 MiB: 1024.00000 Copy: 5405.491 MiB/s AVG Method: MEMCPY Elapsed: 0.18942 MiB: 1024.00000 Copy: 5406.024 MiB/s 0 Method: DUMB Elapsed: 0.14838 MiB: 1024.00000 Copy: 6901.200 MiB/s 1 Method: DUMB Elapsed: 0.14818 MiB: 1024.00000 Copy: 6910.561 MiB/s 2 Method: DUMB Elapsed: 0.14820 MiB: 1024.00000 Copy: 6909.628 MiB/s AVG Method: DUMB Elapsed: 0.14825 MiB: 1024.00000 Copy: 6907.127 MiB/s 0 Method: MCBLOCK Elapsed: 0.04362 MiB: 1024.00000 Copy: 23477.623 MiB/s 1 Method: MCBLOCK Elapsed: 0.04262 MiB: 1024.00000 Copy: 24025.151 MiB/s 2 Method: MCBLOCK Elapsed: 0.04258 MiB: 1024.00000 Copy: 24048.849 MiB/s AVG Method: MCBLOCK Elapsed: 0.04294 MiB: 1024.00000 Copy: 23847.599 MiB/s For reference here's what I get on my Intel based laptop: laptop:~$ mbw -n 3 1024 Long uses 8 bytes. Allocating 2*134217728 elements = 2147483648 bytes of memory. Using 262144 bytes as blocks for memcpy block copy test. Getting down to business... Doing 3 runs per test. 0 Method: MEMCPY Elapsed: 0.40566 MiB: 1024.00000 Copy: 2524.269 MiB/s 1 Method: MEMCPY Elapsed: 0.38458 MiB: 1024.00000 Copy: 2662.638 MiB/s 2 Method: MEMCPY Elapsed: 0.38876 MiB: 1024.00000 Copy: 2634.043 MiB/s AVG Method: MEMCPY Elapsed: 0.39300 MiB: 1024.00000 Copy: 2605.600 MiB/s 0 Method: DUMB Elapsed: 0.30707 MiB: 1024.00000 Copy: 3334.745 MiB/s 1 Method: DUMB Elapsed: 0.30425 MiB: 1024.00000 Copy: 3365.653 MiB/s 2 Method: DUMB Elapsed: 0.30342 MiB: 1024.00000 Copy: 3374.849 MiB/s AVG Method: DUMB Elapsed: 0.30491 MiB: 1024.00000 Copy: 3358.328 MiB/s 0 Method: MCBLOCK Elapsed: 0.07875 MiB: 1024.00000 Copy: 13003.670 MiB/s 1 Method: MCBLOCK Elapsed: 0.08374 MiB: 1024.00000 Copy: 12228.034 MiB/s 2 Method: MCBLOCK Elapsed: 0.07635 MiB: 1024.00000 Copy: 13411.216 MiB/s AVG Method: MCBLOCK Elapsed: 0.07961 MiB: 1024.00000 Copy: 12862.006 MiB/s So according to mbw my laptop is 3 times faster than the server!!! Please help me explain this. I've also tried to mount a ram disk and use dd to benchmark it and I get similar differences so I don't think mbw is to blame. I've checked the BIOS settings and the memory seem to be running at full speed. According to the hosting company the modules are all OK. Could this have something to do with NUMA? It seems like Node Interleaving is disabled on this server. Will enabling it (thus turning off NUMA) make a difference? foo1:~# numactl --hardware available: 4 nodes (0-3) node 0 cpus: 0 1 2 3 4 5 node 0 size: 8190 MB node 0 free: 7898 MB node 1 cpus: 6 7 8 9 10 11 node 1 size: 12288 MB node 1 free: 12073 MB node 2 cpus: 18 19 20 21 22 23 node 2 size: 12288 MB node 2 free: 12034 MB node 3 cpus: 12 13 14 15 16 17 node 3 size: 8192 MB node 3 free: 8032 MB node distances: node 0 1 2 3 0: 10 20 20 20 1: 20 10 20 20 2: 20 20 10 20 3: 20 20 20 10