On Tue, 16 Jun 2015, Jesper Dangaard Brouer wrote: > It is very important that everybody realizes that the save+restore > variant is very expensive, this is key: > > CPU: i7-4790K CPU @ 4.00GHz > * local_irq_{disable,enable}: 7 cycles(tsc) - 1.821 ns > * local_irq_{save,restore} : 37 cycles(tsc) - 9.443 ns > > Even if EVERY object need to call slowpath/__slab_free() it will be > faster than calling the fallback. Because I've demonstrated the call > this_cpu_cmpxchg_double() costs 9 cycles. But the cmpxchg also stores a value. You need to add the cost of the store to the cycles. -- 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>