Messages in this thread | | | Date | Mon, 13 Jul 2009 11:18:01 +0800 | From | Shaohua Li <> | Subject | Re: [PATCH] switch free memory back to MIGRATE_MOVABLE |
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On Mon, Jul 13, 2009 at 11:08:14AM +0800, KOSAKI Motohiro wrote: > > On Mon, Jul 13, 2009 at 10:58:03AM +0800, KAMEZAWA Hiroyuki wrote: > > > On Mon, 13 Jul 2009 11:47:46 +0900 (JST) > > > KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> wrote: > > > > > > > > When page is back to buddy and its order is bigger than pageblock_order, we can > > > > > switch its type to MIGRATE_MOVABLE. This can reduce fragmentation. The patch > > > > > has obvious effect when read a block device and then drop caches. > > > > > > > > > > Signed-off-by: Shaohua Li <shaohua.li@intel.com> > > > > > > > > This patch change hot path, but there is no performance mesurement description. > > > > Also, I don't like modification buddy core for only drop caches. > > > > > > > Li, does this patch imply fallback of migration type doesn't work well ? > > > What is the bad case ? > > The page is initialized as migrate_movable, and then switch to reclaimable or > > something else when fallback occurs, but its type remains even the page gets > > freed. When the page gets freed, its type actually can be switch back to movable, > > this is what the patch does. > > This answer is not actual answer. > Why do you think __rmqueue_fallback() doesn't works well? Do you have > any test-case or found a bug by review? I never said __rmqueue_fallback() doesn't work well. The page is already freed, switching back the pageblock to movable might make next page allocation (non-movable) skip this pageblock. So this could potentially reduce fragmentation and improve memory offline. But your guys are right, I have no number if this will impact performance.
Thanks, Shaohua
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