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Diffstat (limited to 'results/classifier/deepseek-2-tmp/output/hypervisor/1856335')
| -rw-r--r-- | results/classifier/deepseek-2-tmp/output/hypervisor/1856335 | 36 |
1 files changed, 0 insertions, 36 deletions
diff --git a/results/classifier/deepseek-2-tmp/output/hypervisor/1856335 b/results/classifier/deepseek-2-tmp/output/hypervisor/1856335 deleted file mode 100644 index 525d3b205..000000000 --- a/results/classifier/deepseek-2-tmp/output/hypervisor/1856335 +++ /dev/null @@ -1,36 +0,0 @@ - -Cache Layout wrong on many Zen Arch CPUs - -AMD CPUs have L3 cache per 2, 3 or 4 cores. Currently, TOPOEXT seems to always map Cache ass if it was an 4-Core per CCX CPU, which is incorrect, and costs upwards 30% performance (more realistically 10%) in L3 Cache Layout aware applications. - -Example on a 4-CCX CPU (1950X /w 8 Cores and no SMT): - - <cpu mode='custom' match='exact' check='full'> - <model fallback='forbid'>EPYC-IBPB</model> - <vendor>AMD</vendor> - <topology sockets='1' cores='8' threads='1'/> - -In windows, coreinfo reports correctly: - -****---- Unified Cache 1, Level 3, 8 MB, Assoc 16, LineSize 64 -----**** Unified Cache 6, Level 3, 8 MB, Assoc 16, LineSize 64 - -On a 3-CCX CPU (3960X /w 6 cores and no SMT): - - <cpu mode='custom' match='exact' check='full'> - <model fallback='forbid'>EPYC-IBPB</model> - <vendor>AMD</vendor> - <topology sockets='1' cores='6' threads='1'/> - -in windows, coreinfo reports incorrectly: - -****-- Unified Cache 1, Level 3, 8 MB, Assoc 16, LineSize 64 -----** Unified Cache 6, Level 3, 8 MB, Assoc 16, LineSize 64 - - -Validated against 3.0, 3.1, 4.1 and 4.2 versions of qemu-kvm. - -With newer Qemu there is a fix (that does behave correctly) in using the dies parameter: - <qemu:arg value='cores=3,threads=1,dies=2,sockets=1'/> - -The problem is that the dies are exposed differently than how AMD does it natively, they are exposed to Windows as sockets, which means, you can't ever have a machine with more than two CCX (6 cores) as Windows only supports two sockets. (Should this be reported as a separate bug?) \ No newline at end of file |