[PATCH] D37082: [sanitizer] Re-introduce kUseSeparateSizeClassForBatch for the 32-bit Primary

Kostya Kortchinsky via Phabricator via llvm-commits llvm-commits at lists.llvm.org
Fri Aug 25 13:15:28 PDT 2017


cryptoad added a comment.

Latest piece of information: this patch doesn't seem to have a meaningful impact on performances, whether it be single or multi threaded for the 64-bit allocator and 32-bit allocator without batch separation.
For the 32-bit allocator with batch separation enabled (eg: Scudo), this translates to a performance loss of about 2% for a single threaded pure allocation benchmark. A bit less on multi-threaded benchmarks.
This is expected as we are now allocating batches instead of re-using a chunk, but is required to keep the 32-bit allocator safe.
This also translate in a 1MB RSS increase due to the new region allocated for the batches. This is not expected to grow much higher as a single 1MB region can hold 2048 batches (for 512bytes batches).


https://reviews.llvm.org/D37082





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