Add support back for allocation tracking with GC types
Categories
(Core :: JavaScript: WebAssembly, task, P2)
Tracking
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People
(Reporter: rhunt, Unassigned)
References
(Blocks 1 open bug)
Details
Bug 1814519 temporarily is removing support for allocation tracking of GC types while we're optimizing our allocation performance. We'll need to add a dynamic fallback to support allocation tracking for GC types.
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Comment 1•2 years ago
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The severity field is not set for this bug.
:rhunt, could you have a look please?
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Updated•2 years ago
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Comment 2•6 months ago
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Did your struct/array allocation perf patches address this? I think they do a fallback to C++ if their is a AllocationMetadataBuilder on the JSContext, but do we then actually call it?
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Comment 3•6 months ago
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Our MacroAssembler code for wasm structs/arrays increments AllocSite::nurseryAllocCount (see all), and the C++ paths (e.g. here) call site->incAllocCount(). I'm not sure if there is more tracking that needs to be done; I'm not familiar with the whole metadata system.
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Updated•6 months ago
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Comment 4•6 months ago
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The code I was thinking of is the AllocationMetadataBuilder [1] which is a hook that external code (like devtools) can install to add metadata per-object allocated in the system. This was removed to get us a short term perf win, but now that we have better JIT support we should be able to add it back in as a slow path.
So essentially in our JIT code we'd add another check here [2] that sees if cx->allocationMetadataBuilder is enabled, and if so falls back to C++ code. Then in the C++ code we'd wrap our allocation like this [3], and that would set metadata correctly.
[1] https://searchfox.org/mozilla-central/rev/a06d5a8871b1796f2dbd588ab518eaa98507e018/js/src/vm/Realm.h#915
[2] https://searchfox.org/mozilla-central/rev/a06d5a8871b1796f2dbd588ab518eaa98507e018/js/src/jit/MacroAssembler.cpp#6830
[3] https://searchfox.org/mozilla-central/rev/a06d5a8871b1796f2dbd588ab518eaa98507e018/js/src/builtin/MapObject.cpp#741
Description
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