Hi, Minchan, Minchan Kim <minchan@xxxxxxxxxx> writes: > On Fri, Apr 28, 2017 at 09:35:37PM +0800, Huang, Ying wrote: >> In fact, during the test, I found the overhead of sort() is comparable >> with the performance difference of adding likely()/unlikely() to the >> "if" in the function. > > Huang, > > This discussion is started from your optimization code: > > if (nr_swapfiles > 1) > sort(); > > I don't have such fast machine so cannot test it. However, you added > such optimization code in there so I guess it's *worth* to review so > with spending my time, I pointed out what you are missing and > suggested a idea to find a compromise. Sorry for wasting your time and Thanks a lot for your review and suggestion! When I started talking this with you, I found there is some measurable overhead of sort(). But later when I done more tests, I found the measurable overhead is at the same level of likely()/unlikely() compiler notation. So you help me to find that, Thanks again! > Now you are saying sort is so fast so no worth to add more logics > to avoid the overhead? > Then, please just drop that if condition part and instead, sort > it unconditionally. Now, because we found the overhead of sort() is low, I suggest to put minimal effort to avoid it. Like the original implementation, if (nr_swapfiles > 1) sort(); Or, we can make nr_swapfiles more correct as Tim suggested (tracking the number of the swap devices during swap on/off). Best Regards, Huang, Ying -- 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>