Optimise the fast path for alloc and dealloc #62
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This massively improves the TLS access at the expense of not being dynamically loadable.
This is useful as codegen is nicer if we use size_t, but the semantics is uint8_t, and is stored as that in many places in the metadata. Ultimately should introduce a wrapper to check this invariant.
This change introduces a per small sizeclass free list. That can be used to access the free objects for that sizeclass with minimal calculations being required. It changes to a partial bump ptr. We bump allocate a whole OS page worth of objects at a go, so we don't switch as frequently between bump and free list allocation. The code for the fast paths has been restructured to minimise the work required on the common case, and also it is all inlined for the common case. Allocating a zero sized object is moved off the fast path. Ask for 1 byte if you want to be fast.
Fixes GCC warning that was incorrect using an ASSUME. Made fast path and slow path Macros so we can add additional attributes.
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This addresses #58 |
| bool valid_head(bool is_short) | ||
| { | ||
| size_t size = sizeclass_to_size(sizeclass); | ||
| size_t slab_start = get_initial_link(sizeclass, is_short); | ||
| size_t slab_start = get_initial_offset(sizeclass, is_short); | ||
| size_t all_high_bits = ~static_cast<size_t>(1); |
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Didn't we have a constant for this expression?
Removed stub from message queue, and use an actual allocation.
mjp41
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Jul 2, 2019
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Just pushed changes that I think address @davidchisnall s comments
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This seems to have a pretty drastic improvement in speed to heavy allocation benchmarks. It pushes
snmallocto have approximately the same performance asmimallocon thecfracbenchmark.