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On Friday, 24 September 2021 10:06:49 BST Peter Humphrey wrote: |
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> On Thursday, 23 September 2021 19:20:52 BST Michael wrote: |
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> > Out of interest, have you tried booting a NUMA enabled kernel to see what |
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> > dmesg reports? |
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> |
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> Yes, it's been enabled ever since I had a dual-socket motherboard, years |
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> ago. I didn't understand why I did or didn't need it until I read Miles's |
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> post yesterday (thanks, Miles). I don't know why it hadn't been made clear |
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> in any websites I've visited. |
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> |
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> > On an old laptop, which definitely has only a single AMD |
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> > APU, I get: |
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> > |
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> > $ dmesg | grep -i NUMA -A2 |
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> > [ 0.002078] No NUMA configuration found |
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> > [ 0.002080] Faking a node at [mem |
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> |
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> 0x0000000000000000-0x000000042effffff] |
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> |
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> > [ 0.002085] NODE_DATA(0) allocated [mem 0x42effc000-0x42effffff] |
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> |
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> I had something similar. Oddly, with NUMA configured I get "not found" and |
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> without it I get "pci_bus 0000:00: on NUMA node 0". The system seems to run |
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> happily either way. |
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Sorry I should have made it clear - the above "No NUMA configuration found" |
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message was obtained *with* NUMA enabled in my kernel. |
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I suppose "NUMA on node 0" is the default first socket, which the kernel sets |
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up. If the kernel can't find a second CPU it will be 'faking' a multi-CPU |
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memory allocation setup, when it comes to allocate memory to the only CPU |
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available. If the kernel does not have NUMA enabled then it doesn't need to |
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fake anything. It will treat the hardware as a single socket MoBo and no |
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further tests would be undertaken. All suppositions of course, I haven't |
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looked at the code. ;-) |
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