On Mon, Aug 17, 2020 at 8:22 PM Wei Yang <richard.weiyang@xxxxxxxxxxxxxxxxx> wrote: > > On Mon, Aug 17, 2020 at 09:05:32AM -0700, Alexander Duyck wrote: > > > > > >On 8/17/2020 2:35 AM, David Hildenbrand wrote: > >> On 17.08.20 10:48, Wei Yang wrote: > >> > If "page" is the list head, list_for_each_entry_safe() would stop > >> > iteration. > >> > > >> > Signed-off-by: Wei Yang <richard.weiyang@xxxxxxxxxxxxxxxxx> > >> > --- > >> > mm/page_reporting.c | 2 +- > >> > 1 file changed, 1 insertion(+), 1 deletion(-) > >> > > >> > diff --git a/mm/page_reporting.c b/mm/page_reporting.c > >> > index 3bbd471cfc81..aaaa3605123d 100644 > >> > --- a/mm/page_reporting.c > >> > +++ b/mm/page_reporting.c > >> > @@ -178,7 +178,7 @@ page_reporting_cycle(struct page_reporting_dev_info *prdev, struct zone *zone, > >> > * the new head of the free list before we release the > >> > * zone lock. > >> > */ > >> > - if (&page->lru != list && !list_is_first(&page->lru, list)) > >> > + if (!list_is_first(&page->lru, list)) > >> > list_rotate_to_front(&page->lru, list); > >> > /* release lock before waiting on report processing */ > >> > > >> > >> Is this a fix or a cleanup? If it's a fix, can this be reproduced easily > >> and what ere the effects? > >> > > > >This should be a clean-up. Since the &page->lru != list will always be true. > > > >If I recall at some point the that was a check for &next->lru != list but I > >think I pulled out an additional conditional check somewhere so that we just > >go through the start of the loop again and iterate over reported pages until > >we are guaranteed to have a non-reported page to rotate to the top of the > >list with the general idea being that we wanted the allocator to pull > >non-reported pages before reported pages. > > Hi, Alexander, > > I see you mentioned in the changelog, this change "mm/page_reporting: rotate > reported pages to the tail of the list" brings some performance gain. > > Would you mind sharing more test detail? I would like to have a try at my > side. > > Thanks :-) I seem to recall my default test for most of this was the page_fault1 test from the will-it-scale suite of tests. Basically I was running that while leaving page reporting enabled. However I don't know how much visibility you would have into the performance impact as I seem to recall I had to modify the frequency of scheduling for the reporting polling task in order to see much of an impact. Thanks. - Alex
