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src: use v8::LocalVector instead of MaybeStackBuffer<Value> #54934
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Did you benchmark this? The point of
MaybeStackBuffer
is to avoid an extra heap allocation, as the name implies, a benefit that gets lost when switching toLocalVector
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I think we probably don't have a choice according to https://chromium-review.googlesource.com/c/v8/v8/+/4905902 - the
Local
handles are not supposed to be heap-allocated in the usual fashion, so aMaybeStackBuffer<Local<>>
that heap-allocates (when the size > kStackStorageSize) is invalid in the first place and we were probably just being lucky to dodge some memory failures that could be caused by it (or maybe we'll get hit when V8 enables conservative stack scanning).LocalVector
was added as a V8-acknowledged way to properly heap allocate them.There was a problem hiding this comment.
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Although, another way to go with this while preserving the stack-allocation part may be to add a different
MaybeStackBuffer
that usesLocalVector
when it goes heap-allocated, or add some specialization toMaybeStackBuffer
so that the heap-allocated part usesLocalVector
when the element type isLocal
(seems messier though).There was a problem hiding this comment.
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@joyeecheung Yeah, those sound like good ideas for solving this problem to me 🙂
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Q: How can we disallow heap allocation on Local handles? What's the best way?
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targos@0982497
It breaks the world: https://ci.nodejs.org/view/All/job/node-test-commit-arm-debug/15086/nodes=ubuntu2204_debug-arm64/console
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Let's see if it breaks here as well. Thanks for the tip @targos: cloudflare/workerd#2752