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[mimalloc] Remove no-longer-needed limit on emmalloc alignment #21905

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Merged
kripken merged 1 commit into from
May 7, 2024
Merged

[mimalloc] Remove no-longer-needed limit on emmalloc alignment #21905

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12 changes: 2 additions & 10 deletions system/lib/mimalloc/src/prim/emscripten/prim.c
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Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
/* ----------------------------------------------------------------------------
Copyright (c) 2018-2023, Microsoft Research, Daan Leijen
Copyright (c) 2018-2023, Microsoft Research, Daan Leijen, Alon Zakai
This is free software; you can redistribute it and/or modify it under the
terms of the MIT license. A copy of the license can be found in the file
"LICENSE" at the root of this distribution.
Expand Down Expand Up @@ -78,17 +78,10 @@ int _mi_prim_alloc(size_t size, size_t try_alignment, bool commit, bool allow_la
// That assumes no one else uses sbrk but us (they could go up,
// scribble, and then down), but we could assert on that perhaps.
*is_zero = false;
// emmalloc has some limitations on alignment size.
// TODO: Why does mimalloc ask for an align of 4MB? that ends up allocating
// 8, which wastes quite a lot for us in wasm. If that is unavoidable,
// we may want to improve emmalloc to support such alignment. See also
// https://github.com/emscripten-core/emscripten/issues/20645
// emmalloc has a minimum alignment size.
#define MIN_EMMALLOC_ALIGN 8
#define MAX_EMMALLOC_ALIGN (1024*1024)
if (try_alignment < MIN_EMMALLOC_ALIGN) {
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@sbc100 sbc100 May 7, 2024

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Can try_alignment ever be lower than 8 in mimalloc?

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@kripken kripken May 7, 2024

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I think no, since it makes that assumption internally. But we could probably make it do the clamping itself silently, I suppose.

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@kripken kripken May 7, 2024

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Oh sorry, you said mimalloc and I read that as emmalloc. I'm not sure. The initial allocations are definitely 4MB-sized, but there may be other incidental allocations in theory in the codebase somewhere.

try_alignment = MIN_EMMALLOC_ALIGN;
} else if (try_alignment > MAX_EMMALLOC_ALIGN) {
try_alignment = MAX_EMMALLOC_ALIGN;
}
void* p = emmalloc_memalign(try_alignment, size);
*addr = p;
Expand Down Expand Up @@ -249,4 +242,3 @@ void _mi_prim_thread_associate_default_heap(mi_heap_t* heap) {

}
#endif