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| author | Christian Krinitsin <mail@krinitsin.com> | 2025-07-03 16:27:09 +0000 |
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| committer | Christian Krinitsin <mail@krinitsin.com> | 2025-07-03 16:27:09 +0000 |
| commit | 4d9e26c0333abd39bdbd039dcdb30ed429c475ba (patch) | |
| tree | 4010d5fb3e8bc48c110a2c1ff2a16b8648cb86bb /results/classifier/accel-gemma3:12b/vmm/2848 | |
| parent | 5541099586dbd6018574cb44e1934907c121526f (diff) | |
| download | emulator-bug-study-4d9e26c0333abd39bdbd039dcdb30ed429c475ba.tar.gz emulator-bug-study-4d9e26c0333abd39bdbd039dcdb30ed429c475ba.zip | |
add gemma accelerator classification results
Diffstat (limited to 'results/classifier/accel-gemma3:12b/vmm/2848')
| -rw-r--r-- | results/classifier/accel-gemma3:12b/vmm/2848 | 14 |
1 files changed, 14 insertions, 0 deletions
diff --git a/results/classifier/accel-gemma3:12b/vmm/2848 b/results/classifier/accel-gemma3:12b/vmm/2848 new file mode 100644 index 00000000..33a44783 --- /dev/null +++ b/results/classifier/accel-gemma3:12b/vmm/2848 @@ -0,0 +1,14 @@ + +i386 max_cpus off by one +Description of problem: +X86 VMs are currently limited to 255 vCPUs (`mc->max_cpus = 255;` in `pc.c`). +The first occurrence i can find of this limit is in d3e9db933f416c9f1c04df4834d36e2315952e42 from 2005 where both `MAX_APICS` and `MAX_CPUS` was set to 255. This is becoming relevant for some people as servers with 256 cores become more available. + +**Can we increase the limit to 256 vCPUs?** +I think so. + +Today, the APIC id limit (see `apic_id_limit` in `x86-common.c`) is based on the CPU id limit. +According to the a comment for `typdef uint32_t apic_id_t;` (see `topology.h`), we can have 256 APICs, but more APICs require x2APIC support. +APIC seems to be no hindrance to increase max_cpus to 256. + +**Can we increase the limit to 512?** Maybe not? We need x2APIC support of which i have no clue. Also there is always a performance risk of exceeding the size at which current data structures work efficiently. |