f1b2633936
kmalloc_index is a long series of comparisons. The attempt to replace kmalloc_index with something more efficient like ilog2 failed due to compiler issues with constant folding on gcc 3.3 / powerpc. kmalloc_index()'es long list of comparisons works fine for constant folding since all the comparisons are optimized away. However, SLUB also uses kmalloc_index to determine the slab to use for the __kmalloc_xxx functions. This leads to a large set of comparisons in get_slab(). The patch here allows to get rid of that list of comparisons in get_slab(): 1. If the requested size is larger than 192 then we can simply use fls to determine the slab index since all larger slabs are of the power of two type. 2. If the requested size is smaller then we cannot use fls since there are non power of two caches to be considered. However, the sizes are in a managable range. So we divide the size by 8. Then we have only 24 possibilities left and then we simply look up the kmalloc index in a table. Code size of slub.o decreases by more than 200 bytes through this patch. Signed-off-by: Christoph Lameter <clameter@sgi.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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| .. | ||
| allocpercpu.c | ||
| backing-dev.c | ||
| bootmem.c | ||
| bounce.c | ||
| fadvise.c | ||
| filemap_xip.c | ||
| filemap.c | ||
| filemap.h | ||
| fremap.c | ||
| highmem.c | ||
| hugetlb.c | ||
| internal.h | ||
| Kconfig | ||
| madvise.c | ||
| Makefile | ||
| memory_hotplug.c | ||
| memory.c | ||
| mempolicy.c | ||
| mempool.c | ||
| migrate.c | ||
| mincore.c | ||
| mlock.c | ||
| mmap.c | ||
| mmzone.c | ||
| mprotect.c | ||
| mremap.c | ||
| msync.c | ||
| nommu.c | ||
| oom_kill.c | ||
| page_alloc.c | ||
| page_io.c | ||
| page-writeback.c | ||
| pdflush.c | ||
| prio_tree.c | ||
| quicklist.c | ||
| readahead.c | ||
| rmap.c | ||
| shmem_acl.c | ||
| shmem.c | ||
| slab.c | ||
| slob.c | ||
| slub.c | ||
| sparse.c | ||
| swap_state.c | ||
| swap.c | ||
| swapfile.c | ||
| thrash.c | ||
| tiny-shmem.c | ||
| truncate.c | ||
| util.c | ||
| vmalloc.c | ||
| vmscan.c | ||
| vmstat.c | ||