On Wed, Jan 22, 2014 at 02:05:06PM +0800, Han Pingtian wrote: > On Tue, Jan 21, 2014 at 10:23:51AM +0000, Mel Gorman wrote: > > On Tue, Jan 21, 2014 at 05:38:59PM +0800, Han Pingtian wrote: > > > The testcase 'thp04' of LTP will enable THP, do some testing, then > > > disable it if it wasn't enabled. But this will leave a different value > > > of min_free_kbytes if it has been set by admin. So I think it's better > > > to restore the user defined value after disabling THP. > > > > > > > Then have LTP record what min_free_kbytes was at the same time THP was > > enabled by the test and restore both settings. It leaves a window where > > an admin can set an alternative value during the test but that would also > > invalidate the test in same cases and gets filed under "don't do that". > > > > Because the value is changed in kernel, so it would be better to > restore it in kernel, right? :) I have a v2 patch which will restore > the value only if it isn't set again by user after THP's initialization. > This v2 patch is dependent on the patch 'mm: show message when updating > min_free_kbytes in thp' which has been added to -mm tree, can be found > here: > It still feels like the type of scenario that only shows up during tests that modify kernel parameters as part of the test. I do not consider it normal operation for THP to be enabled and disabled multiple types during the lifetime of the system. If the system started with THP disabled, ran for a long period of time then the benefit of having min_free_kbytes at a higher value is already lost due to the system being potentially in a fragmented state already. I'm ok with the warning being displayed if min_free_kbytes is updated but I'm not convinced that further trickery is necessary. -- Mel Gorman SUSE Labs -- 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>