On Wed, May 18, 2016 at 10:22:59AM +0900, Minchan Kim wrote: > On Tue, May 17, 2016 at 03:32:46PM +0300, Kirill A. Shutemov wrote: > > Currently, faultaround code produces young pte. This can screw up vmscan > > behaviour[1], as it makes vmscan think that these pages are hot and not > > push them out on first round. > > > > Let modify faultaround to produce old pte, so they can easily be > > reclaimed under memory pressure. > > > > This can to some extend defeat purpose of faultaround on machines > > without hardware accessed bit as it will not help up with reducing > > number of minor page faults. > > > > We may want to disable faultaround on such machines altogether, but > > that's subject for separate patchset. > > > > [1] https://lkml.kernel.org/r/1460992636-711-1-git-send-email-vinmenon@xxxxxxxxxxxxxx > > > > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> > > Cc: Mel Gorman <mgorman@xxxxxxx> > > Cc: Rik van Riel <riel@xxxxxxxxxx> > > Cc: Michal Hocko <mhocko@xxxxxxxxxx> > > Cc: Vinayak Menon <vinmenon@xxxxxxxxxxxxxx> > > Cc: Minchan Kim <minchan@xxxxxxxxxx> > > I tested 512M mmap sequential word read test on non-HW access bit system > (i.e., ARM) and confirmed it doesn't increase minor fault any more. > > = old = > minor fault: 131291 > elapsed time: 6747645 usec > > = new = > minor fault: 131291 > elapsed time: 6709263 usec > > 0.56% benefit > > Acked-by: Minchan Kim <minchan@xxxxxxxxxx> Oops, label was wrong. I meant old : 4096 fault_around new : 65536 fault_around -- 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>