On Wed, 1 Jun 2016 17:24:24 +0100 Russell King - ARM Linux <[email protected]> wrote:
> On Mon, May 30, 2016 at 11:14:46AM +0200, Michal Hocko wrote: > > From: Michal Hocko <[email protected]> > > > > __GFP_REPEAT has a rather weak semantic but since it has been introduced > > around 2.6.12 it has been ignored for low order allocations. > > > > PGALLOC_GFP uses __GFP_REPEAT but none of the allocation which uses > > this flag is for more than order-2. This means that this flag has never > > been actually useful here because it has always been used only for > > PAGE_ALLOC_COSTLY requests. > > I hear what you say, but... > > commit 8c65da6dc89ccb605d73773b1dd617e72982d971 > Author: Russell King <[email protected]> > Date: Sat Nov 30 12:52:31 2013 +0000 > > ARM: pgd allocation: retry on failure > > Make pgd allocation retry on failure; we really need this to succeed > otherwise fork() can trigger OOMs. > > Signed-off-by: Russell King <[email protected]> > > and that's the change which introduced this, and it did solve a problem > for me. So I'm not happy to give an ack for this change unless someone > can tell me why adding __GFP_REPEAT back then had a beneficial effect. > Maybe there was some other bug in the MM layer in 2013 which this change > happened to solve? I suspect that some other change has made arm's use of __GFP_REPEAT unnecessary, because __GFP_REPEAT is now a no-op for order-0,1,2,3 allocations and none of the arm callsites which I can see are using order-4 or higher. So I think we should go ahead with this change. If that causes some problem then we'll need to dig in and figure out why the impossible just happened, OK?
