-
Notifications
You must be signed in to change notification settings - Fork 1.3k
Commit
This commit does not belong to any branch on this repository, and may belong to a fork outside of the repository.
Lazily populate a store's trampoline map (#3742)
* Lazily populate a store's trampoline map This commit is another installment of "how fast can we make instantiation". Currently when instantiating a module with many function imports each function, typically from the host, is inserted into the store. This insertion process stores the `VMTrampoline` for the host function in a side table so it can be looked up later if the host function is called through the `Func` interface. This insertion process, however, involves a hash map insertion which can be relatively expensive at the scale of the rest of the instantiation process. The optimization implemented in this commit is to avoid inserting trampolines into the store at `Func`-insertion-time (aka instantiation time) and instead only lazily populate the map of trampolines when needed. The theory behind this is that almost all `Func` instances that are called indirectly from the host are actually wasm functions, not host-defined functions. This means that they already don't need to go through the map of host trampolines and can instead be looked up from the module they're defined in. With the assumed rarity of host functions making `lookup_trampoline` a bit slower seems ok. The `lookup_trampoline` function will now, on a miss from the wasm modules and `host_trampolines` map, lazily iterate over the functions within the store and insert trampolines into the `host_trampolines` map. This process will eventually reach something which matches the function provided because it should at least hit the same host function. The relevant `lookup_trampoline` now sports a new documentation block explaining all this as well for future readers. Concretely this commit speeds up instantiation of an empty module with 100 imports and ~80 unique signatures from 10.6us to 6.4us, a 40% improvement. * Review comments * Remove debug assert
- Loading branch information
1 parent
ffa9fe3
commit c839685
Showing
3 changed files
with
96 additions
and
20 deletions.
There are no files selected for viewing
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters