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. ;-)
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