Improve WASI thread id allocator to reuse identifiers by eloparco · Pull Request #1809 · bytecodealliance/wasm-micro-runtime

eloparco · 2022-12-13T17:19:29Z

At the moment, when created, a thread receives an incremental number as an identifier.

This PR allows reusing thread ids once they are released. That is done by using a stack data structure to keep track of the used ids.
When a thread is created, it takes an available identifier from the stack. When the thread exits, it returns the id to the stack of available identifiers.

loganek

Lgtm

eloparco · 2022-12-14T16:37:07Z

I'm doing some additional refactoring to have both pos and size as unsigned so that comparisons are safe. I just need to get pos to point to the first empty position in the stack rather than at the top element.

loganek · 2022-12-15T13:48:59Z

+    if (avail_tids.pos == 0) { // Resize stack and push new thread ids
+        uint32 old_size = avail_tids.size;
+        uint32 new_size = avail_tids.size * 2;
+        if (new_size / 2 != avail_tids.size) {


[minor] you might just compare old_size with the new_size to avoid additional division.

I used the division to make it similar to L54. I'm not sure a simple comparison would work for L54 (maybe when overflowing/wrapping the result can be bigger than the initial value?)

yes, one way to detect integer overflow here is to check if new_size < avail_tids.size. It's not a major callout though.

yamt

looks ok to me

yamt · 2022-12-16T07:36:03Z

+            goto return_id;
+        }
+        int32 *tmp =
+            (int32 *)wasm_runtime_realloc(avail_tids.ids, realloc_size);


you don't need a cast

Should I get rid of it? I put it (and same for the malloc) for consistency with the rest of the codebase

wenyongh

LGTM

@eloparco Can you resolve the conflicts?

eloparco · 2022-12-19T11:29:47Z

@wenyongh fixed the conflicts, I think we can merge it now

…ytecodealliance#1809) This PR allows reusing thread ids once they are released. That is done by using a stack data structure to keep track of the used ids. When a thread is created, it takes an available identifier from the stack. When the thread exits, it returns the id to the stack of available identifiers.

yamt reviewed Dec 14, 2022

View reviewed changes

Comment thread samples/wasi-threads/wasm-apps/CMakeLists.txt

yamt reviewed Dec 14, 2022

View reviewed changes

Comment thread core/iwasm/libraries/lib-wasi-threads/lib_wasi_threads_wrapper.c Outdated

Comment thread core/iwasm/libraries/lib-wasi-threads/lib_wasi_threads_wrapper.c Outdated

Comment thread core/iwasm/libraries/lib-wasi-threads/lib_wasi_threads_wrapper.c Outdated

loganek reviewed Dec 14, 2022

View reviewed changes