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During block processing, we allocate lots and lots of small objects (VertexRef and friends) which causes overhead as the GC is run without much benefit - this can be up to 15% of CPU time during block import when running with a large vertex cache.
arnetheduck
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Jul 3, 2025
Deferred GC seemed like a good idea to reduce the amount of work done during block processing, but a side effect of this is that more memory ends up being allocated in certain workloads which in turn causes an overall slowdown, with a long test showing a net performance effect that hovers around 0% and more memory usage. In particular, the troublesome range around 2M sees a 10-15% slowdown and an ugly memory usage spike. Reverting for now - it might be worth revisiting in the future under different memory allocation patters, but as usual, it's better to not do work at all (like in #3444) than to do work faster. This reverts commit 3a00915.
arnetheduck
added a commit
that referenced
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Jul 4, 2025
Deferred GC seemed like a good idea to reduce the amount of work done during block processing, but a side effect of this is that more memory ends up being allocated in certain workloads which in turn causes an overall slowdown, with a long test showing a net performance effect that hovers around 0% and more memory usage. In particular, the troublesome range around 2M sees a 10-15% slowdown and an ugly memory usage spike. Reverting for now - it might be worth revisiting in the future under different memory allocation patters, but as usual, it's better to not do work at all (like in #3444) than to do work faster. This reverts commit 3a00915.
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During block processing, we allocate lots and lots of small objects (VertexRef and friends) which causes overhead as the GC is run without much benefit - this can be up to 15% of CPU time during block import when running with a large vertex cache.