Disable speculative evaluation in coreprep in ghc 9.4, 9.6, 9.8 #2253
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Speculative evaluation was found to cause a large increase in allocations in certain situations. We disable it for now.
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I've re-enabled some speculative eval while keeping the problematic ones disabled. 9.10 patch will follow soon. I think the condition can still be refined more. |
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We plan to get this fix in the next 9.6 maintenance release (likely late 2024), but the patch may change a bit since it can affect performance of other code. We're not yet sure if unconditionally disabling speculation for dictionary functions is the optimal thing. If there's no optimal choice for all code, we'll add a flag to GHC 9.6.7 (and higher) to control the speculation behaviour. |
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Speculative evaluation was found to cause a large increase in allocations in certain situations.
This should fix the regression we saw in cardano-node: increased allocations and cpu time during mempool snapshotting.