| 1 |
On 24/9/21 5:38 pm, Michael wrote: |
| 2 |
> On Friday, 24 September 2021 10:06:49 BST Peter Humphrey wrote: |
| 3 |
>> On Thursday, 23 September 2021 19:20:52 BST Michael wrote: |
| 4 |
>>> Out of interest, have you tried booting a NUMA enabled kernel to see what |
| 5 |
>>> dmesg reports? |
| 6 |
>> Yes, it's been enabled ever since I had a dual-socket motherboard, years |
| 7 |
>> ago. I didn't understand why I did or didn't need it until I read Miles's |
| 8 |
>> post yesterday (thanks, Miles). I don't know why it hadn't been made clear |
| 9 |
>> in any websites I've visited. |
| 10 |
>> |
| 11 |
>>> On an old laptop, which definitely has only a single AMD |
| 12 |
>>> APU, I get: |
| 13 |
>>> |
| 14 |
>>> $ dmesg | grep -i NUMA -A2 |
| 15 |
>>> [ 0.002078] No NUMA configuration found |
| 16 |
>>> [ 0.002080] Faking a node at [mem |
| 17 |
>> 0x0000000000000000-0x000000042effffff] |
| 18 |
>> |
| 19 |
>>> [ 0.002085] NODE_DATA(0) allocated [mem 0x42effc000-0x42effffff] |
| 20 |
>> I had something similar. Oddly, with NUMA configured I get "not found" and |
| 21 |
>> without it I get "pci_bus 0000:00: on NUMA node 0". The system seems to run |
| 22 |
>> happily either way. |
| 23 |
> Sorry I should have made it clear - the above "No NUMA configuration found" |
| 24 |
> message was obtained *with* NUMA enabled in my kernel. |
| 25 |
> |
| 26 |
> I suppose "NUMA on node 0" is the default first socket, which the kernel sets |
| 27 |
> up. If the kernel can't find a second CPU it will be 'faking' a multi-CPU |
| 28 |
> memory allocation setup, when it comes to allocate memory to the only CPU |
| 29 |
> available. If the kernel does not have NUMA enabled then it doesn't need to |
| 30 |
> fake anything. It will treat the hardware as a single socket MoBo and no |
| 31 |
> further tests would be undertaken. All suppositions of course, I haven't |
| 32 |
> looked at the code. ;-) |
| 33 |
|
| 34 |
Try "numactl --hardware" (from the numactl package) |
| 35 |
|
| 36 |
rattus ~ # numactl --hardware |
| 37 |
available: 1 nodes (0) |
| 38 |
node 0 cpus: 0 1 2 3 4 5 6 7 8 9 10 11 |
| 39 |
node 0 size: 31942 MB |
| 40 |
node 0 free: 7210 MB |
| 41 |
node distances: |
| 42 |
node 0 |
| 43 |
0: 10 |
| 44 |
rattus ~ # |
| 45 |
|
| 46 |
(Intel 6 core - NUMA emulation in the kernel.) |
| 47 |
|
| 48 |
I can only find testing NUMA code and hardware as a reason to have |
| 49 |
emulation enabled on a non-NUMA system? |
| 50 |
|
| 51 |
BillK |
Archives