Enable SCC disclaiming and tweak GC DNSS for InstantOn #20568
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amicic
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Nov 12, 2024
runtime/gc_modron_startup/mminit.cpp
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| #endif /* defined(J9VM_OPT_CRIU_SUPPORT) */ | ||
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this is somewhat an ok place to deal with this, but since these fields are already initially set in OMR's MM_ConfigurationGenerational::initialize(), the matching place in J9 to override the values would be MM_ConfigurationDelegate::initialize()
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Thanks, I agree it's a better place. Fixed.
mpirvu
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Nov 12, 2024
This patch reduces minTimeBetweenMemoryDisclaims from 5000 to 500 and increases the time between disclaims for the data cache, code cache, and iprofiler data by a factor of 10 to maintain the current behavior. For the SCC it removes the scaling of minTimeBetweenMemoryDisclaims such that we will disclaim the SCC every 500 ms. Signed-off-by: Younes Manton <[email protected]>
This patch enables SCC disclaiming when CRIU or CRaC support is enabled. Signed-off-by: Younes Manton <[email protected]>
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This patch scales dnssExpectedRatioMaximum and dnssExpectedRatioMinimum by 2x when neither is user-specified and either CRIU or CRaC support is enabled. This favours reduced memory consumption at the expense of GC overhead. Signed-off-by: Younes Manton <[email protected]>
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amicic
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Nov 13, 2024
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jenkins test sanity xlinux,plinux,zlinux,aix jdk21 |
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I started jenkins sanity tests assuming @amicic will agree with the new version of the code. |
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This PR includes patches that will
dnssExpectedRatioMaximumanddnssExpectedRatioMinimumto be 2x larger when CRIU or CRaC support is enabled. Increasing this threshold favours reducing nursery expansion and average memory consumption at the cost of increased GC overhead.SCC disclaiming increases scavenge times, which causes nursery expansion, and offsets most of the memory savings we get from disclaiming the SCC, hence the adjustment to the thresholds. Another way to tackle this problem is to reduce the impact of SCC disclaim on scavenge by re-organizing the SCC layout or caching the SCC data touched during scavenge separately, but these options require further development to realize.
See #20498 for additional background info on SCC disclaiming.
FYI @vijaysun-omr @mpirvu @amicic