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optimize dynamic allocation alignment #17092

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thestinger opened this issue Sep 8, 2014 · 2 comments
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optimize dynamic allocation alignment #17092

thestinger opened this issue Sep 8, 2014 · 2 comments
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@thestinger
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I-slow Issue: Problems and improvements with respect to performance of generated code.

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@thestinger
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The non-jemalloc allocator implementation should branch on the Rust end in order to use malloc / realloc / free. It will optimize out in essentially every real-world case, since alignment is rarely dynamic.

Exposing functions without the alignment parameter may also make sense, and having a branch on the Rust side for jemalloc would eliminate a branch for the low alignment case inside the allocator.
@thestinger thestinger added the I-slow Issue: Problems and improvements with respect to performance of generated code. label Sep 8, 2014
@thestinger thestinger self-assigned this Sep 8, 2014
@thestinger thestinger changed the title optimize dynamic allocation alignment optimize dynamic allocation alignment for the non-jemalloc case Sep 8, 2014
@huonw
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huonw commented Sep 8, 2014

Does this apply to the size also?

@thestinger thestinger changed the title optimize dynamic allocation alignment for the non-jemalloc case optimize dynamic allocation alignment Sep 8, 2014
@thestinger
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@huonw: It's just an issue for non-standard alignment, since jemalloc needs to do a branch to support it. For a --disable-jemalloc build, a non-standard alignment is a bigger problem. It's just a small micro-optimization, but I happen to be looking into micro-optimizing allocation right now so every little thing counts. In theory, Rust could also do the size calculation statically and have a non-standard hole in the jemalloc API... but we can get to that kind of thing later.

@thestinger thestinger mentioned this issue Sep 8, 2014
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bors added a commit that referenced this issue Sep 10, 2014
@bors
auto merge of #17095 : thestinger/rust/alloc, r=alexcrichton
8eee1b4 
Previously, some parts of this optimization were impossible because the
alignment passed to the free function was not correct. That was fully
fixed by #17012.

Closes #17092
lnicola pushed a commit to lnicola/rust that referenced this issue Apr 20, 2024
@bors
Auto merge of rust-lang#17092 - Veykril:per-queries, r=Veykril
fa67f9a 
minor: Update `per_query_memory_usage` query listing
lnicola pushed a commit to lnicola/rust that referenced this issue Apr 20, 2024
@bors
Auto merge of rust-lang#17092 - Veykril:per-queries, r=Veykril
b256807 
minor: Update `per_query_memory_usage` query listing
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micro-optimize dynamic allocation alignment
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@huonw @thestinger