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85 lines
2.3 KiB
C
85 lines
2.3 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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// Copyright (C) 2013 Andrea Mazzoleni
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#ifndef __RAID_MEMORY_H
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#define __RAID_MEMORY_H
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/**
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* Memory alignment provided by raid_malloc().
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*
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* It should guarantee good cache performance everywhere.
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*/
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#define RAID_MALLOC_ALIGN 256
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/**
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* Memory displacement to avoid cache address sharing on contiguous blocks,
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* used by raid_malloc_vector().
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*
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* When allocating a sequence of blocks with a size of power of 2,
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* there is the risk that the addresses of each block are mapped into the
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* same cache line and prefetching predictor, resulting in a lot of cache
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* sharing if you access all the blocks in parallel, from the start to the
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* end.
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*
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* To avoid this effect, it's better if all the blocks are allocated
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* with a fixed displacement trying to reduce the cache address sharing.
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*
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* The selected displacement was chosen empirically with some speed tests
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* with 8/12/16/20/24 data buffers of 256 KB.
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*
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* These are the results in MB/s with no displacement:
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*
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* sse2
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* gen1 15368 [MB/s]
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* gen2 6814 [MB/s]
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* genz 3033 [MB/s]
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*
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* These are the results with displacement, resulting in improvements
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* in the order of 20% or more:
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*
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* sse2
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* gen1 21936 [MB/s]
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* gen2 11902 [MB/s]
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* genz 5838 [MB/s]
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*
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*/
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#define RAID_MALLOC_DISPLACEMENT (7*256)
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/**
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* Aligned malloc.
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* Use an alignment suitable for the raid functions.
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*/
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void *raid_malloc(size_t size, void **freeptr);
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/**
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* Arbitrary aligned malloc.
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*/
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void *raid_malloc_align(size_t size, size_t align_size, void **freeptr);
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/**
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* Aligned vector allocation.
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* Use an alignment suitable for the raid functions.
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* Returns a vector of @n pointers, each one pointing to a block of
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* the specified @size.
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* The first @nd elements are reversed in order.
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*/
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void **raid_malloc_vector(int nd, int n, size_t size, void **freeptr);
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/**
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* Arbitrary aligned vector allocation.
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*/
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void **raid_malloc_vector_align(int nd, int n, size_t size, size_t align_size, size_t displacement_size, void **freeptr);
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/**
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* Fills the memory vector with pseudo-random data based on the specified seed.
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*/
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void raid_mrand_vector(unsigned seed, int n, size_t size, void **vv);
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/**
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* Tests the memory vector for RAM problems.
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* If a problem is found, it crashes.
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*/
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int raid_mtest_vector(int n, size_t size, void **vv);
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#endif
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