Lazily allocate the bump-alloc chunk in the externref table #3739
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This is another PR along the lines of "let's squeeze all possible performance we can out of instantiation". Before this PR we would copy, by value, the contents of `VMBuiltinFunctionsArray` into each `VMContext` allocated. This array of function pointers is modestly-sized but growing over time as we add various intrinsics. Additionally it's the exact same for all `VMContext` allocations. This PR attempts to speed up instantiation slightly by instead storing an indirection to the function array. This means that calling a builtin intrinsic is a tad bit slower since it requires two loads instead of one (one to get the base pointer, another to get the actual address). Otherwise though `VMContext` initialization is now simply setting one pointer instead of doing a `memcpy` from one location to another. With some macro-magic this commit also replaces the previous implementation with one that's more `const`-friendly which also gets us compile-time type-checks of libcalls as well as compile-time verification that all libcalls are defined. Overall, as with bytecodealliance#3739, the win is very modest here. Locally I measured a speedup from 1.9us to 1.7us taken to instantiate an empty module with one function. While small at these scales it's still a 10% improvement!
This commit updates the allocation of a `VMExternRefActivationsTable` structure to perform zero malloc memory allocations. Previously it would allocate a page-size of `chunk` plus some space in hash sets for future insertions. The main trick here implemented is that after the first gc during the slow path the fast chunk allocation is allocated and configured. The motivation for this PR is that given our recent work to further refine and optimize the instantiation process this allocation started to show up in a nontrivial fashion. Most modules today never touch this table anyway as almost none of them use reference types, so the time spent allocation and deallocating the table per-store was largely wasted time. Concretely on a microbenchmark this PR speeds up instantiation of a module with one function by 30%, decreasing the instantiation cost from 1.8us to 1.2us. Overall a pretty minor win but when the instantiation times we're measuring start being in the single-digit microseconds this win ends up getting magnified!
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* Don't copy `VMBuiltinFunctionsArray` into each `VMContext` This is another PR along the lines of "let's squeeze all possible performance we can out of instantiation". Before this PR we would copy, by value, the contents of `VMBuiltinFunctionsArray` into each `VMContext` allocated. This array of function pointers is modestly-sized but growing over time as we add various intrinsics. Additionally it's the exact same for all `VMContext` allocations. This PR attempts to speed up instantiation slightly by instead storing an indirection to the function array. This means that calling a builtin intrinsic is a tad bit slower since it requires two loads instead of one (one to get the base pointer, another to get the actual address). Otherwise though `VMContext` initialization is now simply setting one pointer instead of doing a `memcpy` from one location to another. With some macro-magic this commit also replaces the previous implementation with one that's more `const`-friendly which also gets us compile-time type-checks of libcalls as well as compile-time verification that all libcalls are defined. Overall, as with #3739, the win is very modest here. Locally I measured a speedup from 1.9us to 1.7us taken to instantiate an empty module with one function. While small at these scales it's still a 10% improvement! * Review comments
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…alliance#3739) This commit updates the allocation of a `VMExternRefActivationsTable` structure to perform zero malloc memory allocations. Previously it would allocate a page-size of `chunk` plus some space in hash sets for future insertions. The main trick here implemented is that after the first gc during the slow path the fast chunk allocation is allocated and configured. The motivation for this PR is that given our recent work to further refine and optimize the instantiation process this allocation started to show up in a nontrivial fashion. Most modules today never touch this table anyway as almost none of them use reference types, so the time spent allocation and deallocating the table per-store was largely wasted time. Concretely on a microbenchmark this PR speeds up instantiation of a module with one function by 30%, decreasing the instantiation cost from 1.8us to 1.2us. Overall a pretty minor win but when the instantiation times we're measuring start being in the single-digit microseconds this win ends up getting magnified!
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…lliance#3741) * Don't copy `VMBuiltinFunctionsArray` into each `VMContext` This is another PR along the lines of "let's squeeze all possible performance we can out of instantiation". Before this PR we would copy, by value, the contents of `VMBuiltinFunctionsArray` into each `VMContext` allocated. This array of function pointers is modestly-sized but growing over time as we add various intrinsics. Additionally it's the exact same for all `VMContext` allocations. This PR attempts to speed up instantiation slightly by instead storing an indirection to the function array. This means that calling a builtin intrinsic is a tad bit slower since it requires two loads instead of one (one to get the base pointer, another to get the actual address). Otherwise though `VMContext` initialization is now simply setting one pointer instead of doing a `memcpy` from one location to another. With some macro-magic this commit also replaces the previous implementation with one that's more `const`-friendly which also gets us compile-time type-checks of libcalls as well as compile-time verification that all libcalls are defined. Overall, as with bytecodealliance#3739, the win is very modest here. Locally I measured a speedup from 1.9us to 1.7us taken to instantiate an empty module with one function. While small at these scales it's still a 10% improvement! * Review comments
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This commit updates the allocation of a
VMExternRefActivationsTablestructure to perform zero malloc memory allocations. Previously it would
allocate a page-size of
chunkplus some space in hash sets for futureinsertions. The main trick here implemented is that after the first gc
during the slow path the fast chunk allocation is allocated and
configured.
The motivation for this PR is that given our recent work to further
refine and optimize the instantiation process this allocation started to
show up in a nontrivial fashion. Most modules today never touch this
table anyway as almost none of them use reference types, so the time
spent allocation and deallocating the table per-store was largely wasted
time.
Concretely on a microbenchmark this PR speeds up instantiation of a
module with one function by 30%, decreasing the instantiation cost from
1.8us to 1.2us. Overall a pretty minor win but when the instantiation
times we're measuring start being in the single-digit microseconds this
win ends up getting magnified!