Staging: xvmalloc memory allocator
* Features: - Low metadata overhead (just 4 bytes per object) - O(1) Alloc/Free - except when we have to call system page allocator to get additional memory. - Very low fragmentation: In all tests, xvmalloc memory usage is within 12% of "Ideal". - Pool based allocator: Each pool can grow and shrink. - It maps pages only when required. So, it does not hog vmalloc area which is very small on 32-bit systems. SLUB allocator could not be used due to fragmentation issues: http://code.google.com/p/compcache/wiki/AllocatorsComparison Data here shows kmalloc using ~43% more memory than TLSF and xvMalloc is showed ~2% more space efficiency than TLSF (due to smaller metadata). Creating various kmem_caches can reduce space efficiency gap but still problem of being limited to low memory exists. Also, it depends on allocating higher order pages to reduce fragmentation - this is not acceptable for ramzswap as it is used under memory crunch (its a swap device!). SLOB allocator could not be used do to reasons mentioned here: http://lkml.org/lkml/2009/3/18/210 * Implementation: It uses two-level bitmap search to find free list containing block of correct size. This idea is taken from TLSF (Two-Level Segregate Fit) allocator and is well explained in its paper (see [Links] below). * Limitations: - Poor scalability: No per-cpu data structures (work in progress). [Links] 1. Details and Performance data: http://code.google.com/p/compcache/wiki/xvMalloc http://code.google.com/p/compcache/wiki/xvMallocPerformance 2. TLSF memory allocator: home: http://rtportal.upv.es/rtmalloc/ paper: http://rtportal.upv.es/rtmalloc/files/MRBC_2008.pdf Signed-off-by: Nitin Gupta <ngupta@vflare.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Nitin Gupta
Greg Kroah-Hartman
parent
efdf83c176
commit
644bf7b598
3 changed files with 623 additions and 0 deletions
507
drivers/staging/ramzswap/xvmalloc.c
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507
drivers/staging/ramzswap/xvmalloc.c
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/*
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* xvmalloc memory allocator
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*
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* Copyright (C) 2008, 2009 Nitin Gupta
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*
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* This code is released using a dual license strategy: BSD/GPL
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* You can choose the licence that better fits your requirements.
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*
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* Released under the terms of 3-clause BSD License
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* Released under the terms of GNU General Public License Version 2.0
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*/
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#include <linux/bitops.h>
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#include <linux/errno.h>
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#include <linux/highmem.h>
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#include <linux/init.h>
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#include <linux/string.h>
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#include <linux/slab.h>
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#include "xvmalloc.h"
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#include "xvmalloc_int.h"
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static void stat_inc(u64 *value)
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{
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*value = *value + 1;
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}
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static void stat_dec(u64 *value)
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{
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*value = *value - 1;
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}
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static int test_flag(struct block_header *block, enum blockflags flag)
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{
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return block->prev & BIT(flag);
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}
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static void set_flag(struct block_header *block, enum blockflags flag)
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{
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block->prev |= BIT(flag);
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}
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static void clear_flag(struct block_header *block, enum blockflags flag)
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{
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block->prev &= ~BIT(flag);
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}
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/*
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* Given <page, offset> pair, provide a derefrencable pointer.
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* This is called from xv_malloc/xv_free path, so it
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* needs to be fast.
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*/
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static void *get_ptr_atomic(struct page *page, u16 offset, enum km_type type)
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{
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unsigned char *base;
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base = kmap_atomic(page, type);
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return base + offset;
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}
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static void put_ptr_atomic(void *ptr, enum km_type type)
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{
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kunmap_atomic(ptr, type);
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}
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static u32 get_blockprev(struct block_header *block)
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{
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return block->prev & PREV_MASK;
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}
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static void set_blockprev(struct block_header *block, u16 new_offset)
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{
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block->prev = new_offset | (block->prev & FLAGS_MASK);
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}
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static struct block_header *BLOCK_NEXT(struct block_header *block)
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{
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return (struct block_header *)
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((char *)block + block->size + XV_ALIGN);
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}
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/*
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* Get index of free list containing blocks of maximum size
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* which is less than or equal to given size.
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*/
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static u32 get_index_for_insert(u32 size)
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{
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if (unlikely(size > XV_MAX_ALLOC_SIZE))
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size = XV_MAX_ALLOC_SIZE;
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size &= ~FL_DELTA_MASK;
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return (size - XV_MIN_ALLOC_SIZE) >> FL_DELTA_SHIFT;
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}
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/*
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* Get index of free list having blocks of size greater than
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* or equal to requested size.
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*/
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static u32 get_index(u32 size)
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{
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if (unlikely(size < XV_MIN_ALLOC_SIZE))
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size = XV_MIN_ALLOC_SIZE;
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size = ALIGN(size, FL_DELTA);
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return (size - XV_MIN_ALLOC_SIZE) >> FL_DELTA_SHIFT;
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}
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/**
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* find_block - find block of at least given size
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* @pool: memory pool to search from
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* @size: size of block required
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* @page: page containing required block
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* @offset: offset within the page where block is located.
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*
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* Searches two level bitmap to locate block of at least
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* the given size. If such a block is found, it provides
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* <page, offset> to identify this block and returns index
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* in freelist where we found this block.
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* Otherwise, returns 0 and <page, offset> params are not touched.
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*/
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static u32 find_block(struct xv_pool *pool, u32 size,
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struct page **page, u32 *offset)
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{
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ulong flbitmap, slbitmap;
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u32 flindex, slindex, slbitstart;
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/* There are no free blocks in this pool */
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if (!pool->flbitmap)
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return 0;
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/* Get freelist index correspoding to this size */
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slindex = get_index(size);
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slbitmap = pool->slbitmap[slindex / BITS_PER_LONG];
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slbitstart = slindex % BITS_PER_LONG;
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/*
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* If freelist is not empty at this index, we found the
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* block - head of this list. This is approximate best-fit match.
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*/
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if (test_bit(slbitstart, &slbitmap)) {
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*page = pool->freelist[slindex].page;
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*offset = pool->freelist[slindex].offset;
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return slindex;
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}
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/*
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* No best-fit found. Search a bit further in bitmap for a free block.
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* Second level bitmap consists of series of 32-bit chunks. Search
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* further in the chunk where we expected a best-fit, starting from
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* index location found above.
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*/
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slbitstart++;
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slbitmap >>= slbitstart;
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/* Skip this search if we were already at end of this bitmap chunk */
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if ((slbitstart != BITS_PER_LONG) && slbitmap) {
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slindex += __ffs(slbitmap) + 1;
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*page = pool->freelist[slindex].page;
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*offset = pool->freelist[slindex].offset;
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return slindex;
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}
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/* Now do a full two-level bitmap search to find next nearest fit */
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flindex = slindex / BITS_PER_LONG;
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flbitmap = (pool->flbitmap) >> (flindex + 1);
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if (!flbitmap)
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return 0;
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flindex += __ffs(flbitmap) + 1;
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slbitmap = pool->slbitmap[flindex];
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slindex = (flindex * BITS_PER_LONG) + __ffs(slbitmap);
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*page = pool->freelist[slindex].page;
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*offset = pool->freelist[slindex].offset;
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return slindex;
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}
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/*
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* Insert block at <page, offset> in freelist of given pool.
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* freelist used depends on block size.
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*/
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static void insert_block(struct xv_pool *pool, struct page *page, u32 offset,
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struct block_header *block)
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{
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u32 flindex, slindex;
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struct block_header *nextblock;
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slindex = get_index_for_insert(block->size);
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flindex = slindex / BITS_PER_LONG;
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block->link.prev_page = 0;
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block->link.prev_offset = 0;
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block->link.next_page = pool->freelist[slindex].page;
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block->link.next_offset = pool->freelist[slindex].offset;
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pool->freelist[slindex].page = page;
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pool->freelist[slindex].offset = offset;
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if (block->link.next_page) {
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nextblock = get_ptr_atomic(block->link.next_page,
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block->link.next_offset, KM_USER1);
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nextblock->link.prev_page = page;
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nextblock->link.prev_offset = offset;
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put_ptr_atomic(nextblock, KM_USER1);
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}
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__set_bit(slindex % BITS_PER_LONG, &pool->slbitmap[flindex]);
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__set_bit(flindex, &pool->flbitmap);
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}
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/*
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* Remove block from head of freelist. Index 'slindex' identifies the freelist.
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*/
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static void remove_block_head(struct xv_pool *pool,
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struct block_header *block, u32 slindex)
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{
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struct block_header *tmpblock;
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u32 flindex = slindex / BITS_PER_LONG;
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pool->freelist[slindex].page = block->link.next_page;
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pool->freelist[slindex].offset = block->link.next_offset;
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block->link.prev_page = 0;
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block->link.prev_offset = 0;
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if (!pool->freelist[slindex].page) {
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__clear_bit(slindex % BITS_PER_LONG, &pool->slbitmap[flindex]);
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if (!pool->slbitmap[flindex])
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__clear_bit(flindex, &pool->flbitmap);
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} else {
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/*
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* DEBUG ONLY: We need not reinitialize freelist head previous
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* pointer to 0 - we never depend on its value. But just for
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* sanity, lets do it.
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*/
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tmpblock = get_ptr_atomic(pool->freelist[slindex].page,
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pool->freelist[slindex].offset, KM_USER1);
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tmpblock->link.prev_page = 0;
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tmpblock->link.prev_offset = 0;
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put_ptr_atomic(tmpblock, KM_USER1);
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}
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}
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/*
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* Remove block from freelist. Index 'slindex' identifies the freelist.
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*/
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static void remove_block(struct xv_pool *pool, struct page *page, u32 offset,
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struct block_header *block, u32 slindex)
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{
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u32 flindex;
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struct block_header *tmpblock;
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if (pool->freelist[slindex].page == page
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&& pool->freelist[slindex].offset == offset) {
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remove_block_head(pool, block, slindex);
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return;
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}
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flindex = slindex / BITS_PER_LONG;
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if (block->link.prev_page) {
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tmpblock = get_ptr_atomic(block->link.prev_page,
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block->link.prev_offset, KM_USER1);
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tmpblock->link.next_page = block->link.next_page;
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tmpblock->link.next_offset = block->link.next_offset;
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put_ptr_atomic(tmpblock, KM_USER1);
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}
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if (block->link.next_page) {
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tmpblock = get_ptr_atomic(block->link.next_page,
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block->link.next_offset, KM_USER1);
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tmpblock->link.prev_page = block->link.prev_page;
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tmpblock->link.prev_offset = block->link.prev_offset;
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put_ptr_atomic(tmpblock, KM_USER1);
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}
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}
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/*
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* Allocate a page and add it freelist of given pool.
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*/
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static int grow_pool(struct xv_pool *pool, gfp_t flags)
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{
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struct page *page;
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struct block_header *block;
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page = alloc_page(flags);
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if (unlikely(!page))
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return -ENOMEM;
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stat_inc(&pool->total_pages);
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spin_lock(&pool->lock);
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block = get_ptr_atomic(page, 0, KM_USER0);
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block->size = PAGE_SIZE - XV_ALIGN;
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set_flag(block, BLOCK_FREE);
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clear_flag(block, PREV_FREE);
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set_blockprev(block, 0);
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insert_block(pool, page, 0, block);
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put_ptr_atomic(block, KM_USER0);
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spin_unlock(&pool->lock);
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return 0;
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}
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/*
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* Create a memory pool. Allocates freelist, bitmaps and other
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* per-pool metadata.
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*/
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struct xv_pool *xv_create_pool(void)
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{
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u32 ovhd_size;
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struct xv_pool *pool;
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ovhd_size = roundup(sizeof(*pool), PAGE_SIZE);
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pool = kzalloc(ovhd_size, GFP_KERNEL);
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if (!pool)
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return NULL;
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spin_lock_init(&pool->lock);
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return pool;
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}
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void xv_destroy_pool(struct xv_pool *pool)
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{
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kfree(pool);
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}
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/**
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* xv_malloc - Allocate block of given size from pool.
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* @pool: pool to allocate from
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* @size: size of block to allocate
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* @page: page no. that holds the object
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* @offset: location of object within page
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*
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* On success, <page, offset> identifies block allocated
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* and 0 is returned. On failure, <page, offset> is set to
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* 0 and -ENOMEM is returned.
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*
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* Allocation requests with size > XV_MAX_ALLOC_SIZE will fail.
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*/
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int xv_malloc(struct xv_pool *pool, u32 size, struct page **page,
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u32 *offset, gfp_t flags)
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{
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int error;
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u32 index, tmpsize, origsize, tmpoffset;
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struct block_header *block, *tmpblock;
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*page = NULL;
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*offset = 0;
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origsize = size;
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if (unlikely(!size || size > XV_MAX_ALLOC_SIZE))
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return -ENOMEM;
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size = ALIGN(size, XV_ALIGN);
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spin_lock(&pool->lock);
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index = find_block(pool, size, page, offset);
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if (!*page) {
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spin_unlock(&pool->lock);
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if (flags & GFP_NOWAIT)
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return -ENOMEM;
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error = grow_pool(pool, flags);
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if (unlikely(error))
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return error;
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spin_lock(&pool->lock);
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index = find_block(pool, size, page, offset);
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}
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if (!*page) {
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spin_unlock(&pool->lock);
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return -ENOMEM;
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}
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block = get_ptr_atomic(*page, *offset, KM_USER0);
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remove_block_head(pool, block, index);
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/* Split the block if required */
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tmpoffset = *offset + size + XV_ALIGN;
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tmpsize = block->size - size;
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tmpblock = (struct block_header *)((char *)block + size + XV_ALIGN);
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if (tmpsize) {
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tmpblock->size = tmpsize - XV_ALIGN;
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set_flag(tmpblock, BLOCK_FREE);
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clear_flag(tmpblock, PREV_FREE);
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set_blockprev(tmpblock, *offset);
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if (tmpblock->size >= XV_MIN_ALLOC_SIZE)
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insert_block(pool, *page, tmpoffset, tmpblock);
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if (tmpoffset + XV_ALIGN + tmpblock->size != PAGE_SIZE) {
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tmpblock = BLOCK_NEXT(tmpblock);
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set_blockprev(tmpblock, tmpoffset);
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}
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} else {
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/* This block is exact fit */
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if (tmpoffset != PAGE_SIZE)
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clear_flag(tmpblock, PREV_FREE);
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}
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block->size = origsize;
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clear_flag(block, BLOCK_FREE);
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put_ptr_atomic(block, KM_USER0);
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spin_unlock(&pool->lock);
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*offset += XV_ALIGN;
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return 0;
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}
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/*
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* Free block identified with <page, offset>
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*/
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void xv_free(struct xv_pool *pool, struct page *page, u32 offset)
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{
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void *page_start;
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struct block_header *block, *tmpblock;
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offset -= XV_ALIGN;
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spin_lock(&pool->lock);
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page_start = get_ptr_atomic(page, 0, KM_USER0);
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block = (struct block_header *)((char *)page_start + offset);
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/* Catch double free bugs */
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BUG_ON(test_flag(block, BLOCK_FREE));
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block->size = ALIGN(block->size, XV_ALIGN);
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tmpblock = BLOCK_NEXT(block);
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if (offset + block->size + XV_ALIGN == PAGE_SIZE)
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tmpblock = NULL;
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/* Merge next block if its free */
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if (tmpblock && test_flag(tmpblock, BLOCK_FREE)) {
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/*
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* Blocks smaller than XV_MIN_ALLOC_SIZE
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* are not inserted in any free list.
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*/
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if (tmpblock->size >= XV_MIN_ALLOC_SIZE) {
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remove_block(pool, page,
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offset + block->size + XV_ALIGN, tmpblock,
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get_index_for_insert(tmpblock->size));
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}
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block->size += tmpblock->size + XV_ALIGN;
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}
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/* Merge previous block if its free */
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if (test_flag(block, PREV_FREE)) {
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tmpblock = (struct block_header *)((char *)(page_start) +
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get_blockprev(block));
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offset = offset - tmpblock->size - XV_ALIGN;
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if (tmpblock->size >= XV_MIN_ALLOC_SIZE)
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remove_block(pool, page, offset, tmpblock,
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get_index_for_insert(tmpblock->size));
|
||||
|
||||
tmpblock->size += block->size + XV_ALIGN;
|
||||
block = tmpblock;
|
||||
}
|
||||
|
||||
/* No used objects in this page. Free it. */
|
||||
if (block->size == PAGE_SIZE - XV_ALIGN) {
|
||||
put_ptr_atomic(page_start, KM_USER0);
|
||||
spin_unlock(&pool->lock);
|
||||
|
||||
__free_page(page);
|
||||
stat_dec(&pool->total_pages);
|
||||
return;
|
||||
}
|
||||
|
||||
set_flag(block, BLOCK_FREE);
|
||||
if (block->size >= XV_MIN_ALLOC_SIZE)
|
||||
insert_block(pool, page, offset, block);
|
||||
|
||||
if (offset + block->size + XV_ALIGN != PAGE_SIZE) {
|
||||
tmpblock = BLOCK_NEXT(block);
|
||||
set_flag(tmpblock, PREV_FREE);
|
||||
set_blockprev(tmpblock, offset);
|
||||
}
|
||||
|
||||
put_ptr_atomic(page_start, KM_USER0);
|
||||
spin_unlock(&pool->lock);
|
||||
}
|
||||
|
||||
u32 xv_get_object_size(void *obj)
|
||||
{
|
||||
struct block_header *blk;
|
||||
|
||||
blk = (struct block_header *)((char *)(obj) - XV_ALIGN);
|
||||
return blk->size;
|
||||
}
|
||||
|
||||
/*
|
||||
* Returns total memory used by allocator (userdata + metadata)
|
||||
*/
|
||||
u64 xv_get_total_size_bytes(struct xv_pool *pool)
|
||||
{
|
||||
return pool->total_pages << PAGE_SHIFT;
|
||||
}
|
||||
30
drivers/staging/ramzswap/xvmalloc.h
Normal file
30
drivers/staging/ramzswap/xvmalloc.h
Normal file
|
|
@ -0,0 +1,30 @@
|
|||
/*
|
||||
* xvmalloc memory allocator
|
||||
*
|
||||
* Copyright (C) 2008, 2009 Nitin Gupta
|
||||
*
|
||||
* This code is released using a dual license strategy: BSD/GPL
|
||||
* You can choose the licence that better fits your requirements.
|
||||
*
|
||||
* Released under the terms of 3-clause BSD License
|
||||
* Released under the terms of GNU General Public License Version 2.0
|
||||
*/
|
||||
|
||||
#ifndef _XV_MALLOC_H_
|
||||
#define _XV_MALLOC_H_
|
||||
|
||||
#include <linux/types.h>
|
||||
|
||||
struct xv_pool;
|
||||
|
||||
struct xv_pool *xv_create_pool(void);
|
||||
void xv_destroy_pool(struct xv_pool *pool);
|
||||
|
||||
int xv_malloc(struct xv_pool *pool, u32 size, struct page **page,
|
||||
u32 *offset, gfp_t flags);
|
||||
void xv_free(struct xv_pool *pool, struct page *page, u32 offset);
|
||||
|
||||
u32 xv_get_object_size(void *obj);
|
||||
u64 xv_get_total_size_bytes(struct xv_pool *pool);
|
||||
|
||||
#endif
|
||||
86
drivers/staging/ramzswap/xvmalloc_int.h
Normal file
86
drivers/staging/ramzswap/xvmalloc_int.h
Normal file
|
|
@ -0,0 +1,86 @@
|
|||
/*
|
||||
* xvmalloc memory allocator
|
||||
*
|
||||
* Copyright (C) 2008, 2009 Nitin Gupta
|
||||
*
|
||||
* This code is released using a dual license strategy: BSD/GPL
|
||||
* You can choose the licence that better fits your requirements.
|
||||
*
|
||||
* Released under the terms of 3-clause BSD License
|
||||
* Released under the terms of GNU General Public License Version 2.0
|
||||
*/
|
||||
|
||||
#ifndef _XV_MALLOC_INT_H_
|
||||
#define _XV_MALLOC_INT_H_
|
||||
|
||||
#include <linux/kernel.h>
|
||||
#include <linux/types.h>
|
||||
|
||||
/* User configurable params */
|
||||
|
||||
/* Must be power of two */
|
||||
#define XV_ALIGN_SHIFT 2
|
||||
#define XV_ALIGN (1 << XV_ALIGN_SHIFT)
|
||||
#define XV_ALIGN_MASK (XV_ALIGN - 1)
|
||||
|
||||
/* This must be greater than sizeof(link_free) */
|
||||
#define XV_MIN_ALLOC_SIZE 32
|
||||
#define XV_MAX_ALLOC_SIZE (PAGE_SIZE - XV_ALIGN)
|
||||
|
||||
/* Free lists are separated by FL_DELTA bytes */
|
||||
#define FL_DELTA_SHIFT 3
|
||||
#define FL_DELTA (1 << FL_DELTA_SHIFT)
|
||||
#define FL_DELTA_MASK (FL_DELTA - 1)
|
||||
#define NUM_FREE_LISTS ((XV_MAX_ALLOC_SIZE - XV_MIN_ALLOC_SIZE) \
|
||||
/ FL_DELTA + 1)
|
||||
|
||||
#define MAX_FLI DIV_ROUND_UP(NUM_FREE_LISTS, BITS_PER_LONG)
|
||||
|
||||
/* End of user params */
|
||||
|
||||
enum blockflags {
|
||||
BLOCK_FREE,
|
||||
PREV_FREE,
|
||||
__NR_BLOCKFLAGS,
|
||||
};
|
||||
|
||||
#define FLAGS_MASK XV_ALIGN_MASK
|
||||
#define PREV_MASK (~FLAGS_MASK)
|
||||
|
||||
struct freelist_entry {
|
||||
struct page *page;
|
||||
u16 offset;
|
||||
u16 pad;
|
||||
};
|
||||
|
||||
struct link_free {
|
||||
struct page *prev_page;
|
||||
struct page *next_page;
|
||||
u16 prev_offset;
|
||||
u16 next_offset;
|
||||
};
|
||||
|
||||
struct block_header {
|
||||
union {
|
||||
/* This common header must be ALIGN bytes */
|
||||
u8 common[XV_ALIGN];
|
||||
struct {
|
||||
u16 size;
|
||||
u16 prev;
|
||||
};
|
||||
};
|
||||
struct link_free link;
|
||||
};
|
||||
|
||||
struct xv_pool {
|
||||
ulong flbitmap;
|
||||
ulong slbitmap[MAX_FLI];
|
||||
spinlock_t lock;
|
||||
|
||||
struct freelist_entry freelist[NUM_FREE_LISTS];
|
||||
|
||||
/* stats */
|
||||
u64 total_pages;
|
||||
};
|
||||
|
||||
#endif
|
||||
Reference in a new issue