On Tue, 3 Feb 2015 16:42:14 +0800 "Wang, Yalin" <Yalin.Wang@xxxxxxxxxxxxxx> wrote: > I make a change in kernel to test hit/miss ratio: Neat, thanks. > > ... > > After use the phone some time: > root@D5303:/ # cat /proc/meminfo > VmallocUsed: 10348 kB > VmallocChunk: 75632 kB > __set_bit_miss_count:10002 __set_bit_success_count:1096661 > __clear_bit_miss_count:359484 __clear_bit_success_count:3674617 > __test_and_set_bit_miss_count:7 __test_and_set_bit_success_count:221 > __test_and_clear_bit_miss_count:924611 __test_and_clear_bit_success_count:193 > > __test_and_clear_bit_miss_count has a very high miss rate. > In fact, I think set/clear/test_and_set(clear)_bit atomic version can also > Be investigated to see its miss ratio, > I have not tested the atomic version, > Because it reside in different architectures. Hopefully misses in test_and_X_bit are not a problem. The CPU implementation would be pretty stupid to go and dirty the cacheline when it knows it didn't change anything. But maybe I'm wrong about that. That we're running clear_bit against a cleared bit 10% of the time is a bit alarming. I wonder where that's coming from. The enormous miss count in test_and_clear_bit() might indicate an inefficiency somewhere. -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
