On Mon, 16 Dec 2013, Dave Hansen wrote: > I'll do some testing and see if I can coax out any delta from the > optimization myself. Christoph went to a lot of trouble to put this > together, so I assumed that he had a really good reason, although the > changelogs don't really mention any. The cmpxchg on the struct page avoids disabling interrupts etc and therefore simplifies the code significantly. > I honestly can't imagine that a cmpxchg16 is going to be *THAT* much > cheaper than a per-page spinlock. The contended case of the cmpxchg is > way more expensive than spinlock contention for sure. Make sure slub does not set __CMPXCHG_DOUBLE in the kmem_cache flags and it will fall back to spinlocks if you want to do a comparison. Most non x86 arches will use that fallback code. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>