On 08/15/2017 10:30 AM, Mel Gorman wrote: > On Tue, Aug 15, 2017 at 09:55:39AM -0700, Tim Chen wrote:
>> >> Doubling the threshold and counter size will help, but not as much >> as making them above u8 limit as seen in Kemi's data: >> >> 125 537 358906028 <==> system by default (base) >> 256 468 412397590 >> 32765 394(-26.6%) 488932078(+36.2%) <==> with this patchset >> >> For small system making them u8 makes sense. For larger ones the >> frequent local counter overflow into the global counter still >> causes a lot of cache bounce. Kemi can perhaps collect some data >> to see what is the gain from making the counters u8. >> > > The same comments hold. The increase of a cache line is undesirable but > there are other places where the overall cost can be reduced by special > casing based on how this counter is used (always incrementing by one). Can you be more explicit of what optimization you suggest here and changes to inc/dec_zone_page_state? Seems to me like we will still overflow the local counter with the same frequency unless the threshold and counter size is changed. Thanks. Tim > It would be preferred if those were addressed to see how close that gets > to the same performance of doubling the necessary storage for a counter. > doubling the storage >
