Fix clocktest false failure on high CPU count systems (bugfix)#2539
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Fix clocktest false failure on high CPU count systems (bugfix)#2539mreed8855 wants to merge 1 commit into
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HPE tested this. Testing for clock jitter on 688 cpus Testing clock direction for 5 minutes... |
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On systems with many cores (e.g., 688), the cumulative time spent switching affinity and yielding exceeds MAX_JITTER (0.2s). This causes the test to misidentify loop overhead as clock skew. This patch brackets the sampling loop and normalizes each CPU's timestamp against its relative position in the sequence. This isolates actual hardware jitter from the predictable delay of the measurement loop itself.
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On systems with many cores (e.g., 688), the cumulative time spent switching affinity and yielding exceeds MAX_JITTER (0.2s). This causes the test to misidentify loop overhead as clock skew.
This patch brackets the sampling loop and normalizes each CPU's timestamp against its relative position in the sequence. This isolates actual hardware jitter from the predictable delay of the measurement loop itself.
Description
This patch brackets the sampling loop and normalizes each CPU's timestamp against its relative position in the sequence. This isolates actual hardware jitter from the predictable delay of the measurement loop itself.
Resolved issues
https://bugs.launchpad.net/hp/+bug/2143999
This issue was seen on 26.04 and also on 24.04 but only on systems with high core counts.
Documentation
Tests