2014-12-18 0:36 GMT+09:00 Christoph Lameter <c...@linux.com>: > On Wed, 17 Dec 2014, Joonsoo Kim wrote: > >> Ping... and I found another way to remove preempt_disable/enable >> without complex changes. >> >> What we want to ensure is getting tid and kmem_cache_cpu >> on the same cpu. We can achieve that goal with below condition loop. >> >> I ran Jesper's benchmark and saw 3~5% win in a fast-path loop over >> kmem_cache_alloc+free in CONFIG_PREEMPT. >> >> 14.5 ns -> 13.8 ns >> >> See following patch. > > Good idea. How does this affect the !CONFIG_PREEMPT case?
One more this_cpu_xxx makes fastpath slow if !CONFIG_PREEMPT. Roughly 3~5%. We can deal with each cases separately although it looks dirty. #ifdef CONFIG_PREEMPT XXX #else YYY #endif Thanks. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
