Messages in this thread Patch in this message | | | Subject | Re: slab: avoid linear search in kmalloc? (GCC Guru wanted :) | From | Momchil Velikov <> | Date | 21 Nov 2001 11:14:55 +0200 |
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>>>>> "Bernd" == Bernd Eckenfels <ecki@lina.inka.de> writes:
Bernd> Hello, Bernd> I noticed that kmalloc and kmem_find_general_cachep are doing a linear Bernd> search in the cache_sizes array. Isnt it better to speed that up by doing a Bernd> binary search or a b-tree if like the following patch?
Here is a patch using a gcc extension. gcc generates binary search for the case.
Regards, -velco
--- slab.c.orig Wed Sep 19 00:16:26 2001 +++ slab.c Wed Nov 21 11:11:09 2001 @@ -1533,15 +1533,9 @@ void * kmem_cache_alloc (kmem_cache_t *c */ void * kmalloc (size_t size, int flags) { - cache_sizes_t *csizep = cache_sizes; - - for (; csizep->cs_size; csizep++) { - if (size > csizep->cs_size) - continue; - return __kmem_cache_alloc(flags & GFP_DMA ? - csizep->cs_dmacachep : csizep->cs_cachep, flags); - } - return NULL; + kmem_cache_t *cp = kmem_find_general_cachep (size, flags); + + return cp == NULL ? NULL : __kmem_cache_alloc(cp, flags); } /** @@ -1589,18 +1583,66 @@ void kfree (const void *objp) kmem_cache_t * kmem_find_general_cachep (size_t size, int gfpflags) { - cache_sizes_t *csizep = cache_sizes; + int idx; - /* This function could be moved to the header file, and - * made inline so consumers can quickly determine what - * cache pointer they require. - */ - for ( ; csizep->cs_size; csizep++) { - if (size > csizep->cs_size) - continue; + switch (size) { +#if PAGE_SIZE == 4096 + case 0 ... 32: + idx = 0; + break; + case 33 ... 64: + idx = 1; + break; +#else + case 0 ... 64: + idx = 1; + break; +#endif + case 65 ... 128: + idx = 2; + break; + case 129 ... 256: + idx = 3; + break; + case 257 ...512: + idx = 4; + break; + case 513 ... 1024: + idx = 5; + break; + case 1025 ... 2048: + idx = 6; + break; + case 2049 ... 4096: + idx = 7; + break; + case 4097 ... 8192: + idx = 8; + break; + case 8193 ... 16384: + idx = 9; + break; + case 16385 ... 32768: + idx = 10; + break; + case 32769 ... 65536: + idx = 11; + break; + case 65537 ... 131072: + idx = 12; + break; + default: + idx = -1; break; } - return (gfpflags & GFP_DMA) ? csizep->cs_dmacachep : csizep->cs_cachep; + + if (idx == -1) + return NULL; + +#if PAGE_SIZE != 4096 + idx = idx - 1; +#endif + return (gfpflags & GFP_DMA) ? cache_sizes [idx].cs_dmacachep : cache_sizes [idx].cs_cachep; } #ifdef CONFIG_SMP - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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