On Tue, 8 May 2007, Matt Mackall wrote: > > Exactly. That overhead does not exist in SLUB. Thus SLOB is less efficient > > than SLUB. > > What size object does kmalloc(80) return? In SLAB, the answer is 128 > bytes with 48 bytes of slack space. In SLOB, the answer is 88 for 8 > bytes of slack space. Looks like SLUB is in the same camp as SLAB > here:
There is a 96 sized general slab. So it would go up to that size. But you can create a 80 byte slab of course. And that may cost minimal overhead since 80 byte slabs may be merged. If one already exist then you get it for free. > +/* > + * We keep the general caches in an array of slab caches that are used for > + * 2^x bytes of allocations. > + */ > +extern struct kmem_cache kmalloc_caches[KMALLOC_SHIFT_HIGH + 1]; > .. > + if (size <= 128) return 7; 96 please. You skipped the first part. > SLOB's kmalloc overhead is 8 bytes, always. That's 1/8th the average > SLAB kmalloc overhead. SLUB can generate an 80 byte slab with minimal overhead if you wanted. But yes I agree the flexbility there is an advantage if you have objects of various sizes. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/