* Christoph Lameter <[email protected]> [130508 12:06]: > On Wed, 8 May 2013, Chris Mason wrote: > > > > You correctly moved the checks out of the if (!kmalloc_cacheS()) > > > condition so that the caches are created properly. > > > > But if the ordering is required at all, why is it ok to create cache 2 > > after cache 6 instead of after cache 7? > > The power of two caches are 2^x beginning with KMALLOC_MIN_SHIFT. The non > power of two caches were folded into number 1 + 2 since they do not fit > into the scheme and they are special cased throughout. This works since > the minimal slab cache size is 8 bytes. > > > IOW if we can safely do cache 2 after cache 6, why can't we just do both > > cache 1 and cache 2 after the loop? > > Because the cache creation in SLAB can cause the use of a fractional slab > size if kmem_cache_create() thinks its better to put the metadata on a > different slab cache (OFF_SLAB type) because data will align better that > way. Its weird I know but its due to the way that SLAB aligns data in the > page frame.
Hmm OK so kmalloc_caches[7] got created earlier with INDEX_AC != INDEX_NODE, and those are defined as: #define INDEX_AC kmalloc_index(sizeof(struct arraycache_init)) #define INDEX_NODE kmalloc_index(sizeof(struct kmem_cache_node)) So the different sizes for the structs can trigger it like Pekka was speculating earlier. Regards, Tony -- 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/
