On 24/9/21 7:25 pm, William Kenworthy wrote: > On 24/9/21 5:38 pm, Michael wrote: >> On Friday, 24 September 2021 10:06:49 BST Peter Humphrey wrote: >>> On Thursday, 23 September 2021 19:20:52 BST Michael wrote: >>>> Out of interest, have you tried booting a NUMA enabled kernel to see what >>>> dmesg reports? >>> Yes, it's been enabled ever since I had a dual-socket motherboard, years >>> ago. I didn't understand why I did or didn't need it until I read Miles's >>> post yesterday (thanks, Miles). I don't know why it hadn't been made clear >>> in any websites I've visited. >>> >>>> On an old laptop, which definitely has only a single AMD >>>> APU, I get: >>>> >>>> $ dmesg | grep -i NUMA -A2 >>>> [ 0.002078] No NUMA configuration found >>>> [ 0.002080] Faking a node at [mem >>> 0x0000000000000000-0x000000042effffff] >>> >>>> [ 0.002085] NODE_DATA(0) allocated [mem 0x42effc000-0x42effffff] >>> I had something similar. Oddly, with NUMA configured I get "not found" and >>> without it I get "pci_bus 0000:00: on NUMA node 0". The system seems to run >>> happily either way. >> Sorry I should have made it clear - the above "No NUMA configuration found" >> message was obtained *with* NUMA enabled in my kernel. >> >> I suppose "NUMA on node 0" is the default first socket, which the kernel >> sets >> up. If the kernel can't find a second CPU it will be 'faking' a multi-CPU >> memory allocation setup, when it comes to allocate memory to the only CPU >> available. If the kernel does not have NUMA enabled then it doesn't need to >> fake anything. It will treat the hardware as a single socket MoBo and no >> further tests would be undertaken. All suppositions of course, I haven't >> looked at the code. ;-) > Try "numactl --hardware" (from the numactl package) > > rattus ~ # numactl --hardware > available: 1 nodes (0) > node 0 cpus: 0 1 2 3 4 5 6 7 8 9 10 11 > node 0 size: 31942 MB > node 0 free: 7210 MB > node distances: > node 0 > 0: 10 > rattus ~ # > > (Intel 6 core - NUMA emulation in the kernel.) > > I can only find testing NUMA code and hardware as a reason to have > emulation enabled on a non-NUMA system? > > BillK > > Actually Iam using "numactl -C 4,5 /etc/init.d/amavisd start" to lock processes to particular cpu's (on an arm big.LITTLE architecture.
I will need to compile a new kernel without NUMA emulation to see if it still works. BillK
