On Thu, Sep 29, 2016 at 10:55:44PM +1000, Nicholas Piggin wrote: > On Thu, 29 Sep 2016 10:01:30 +0200 > Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote: > > > On Tue, Sep 27, 2016 at 09:54:12AM +0100, Mel Gorman wrote: > > > On Tue, Sep 27, 2016 at 09:30:55AM +0200, Peter Zijlstra wrote: > > > Simple is relative unless I drastically overcomplicated things and it > > > wouldn't be the first time. 64-bit only side-steps the page flag issue > > > as long as we can live with that. > > > > So one problem with the 64bit only pageflags is that they do eat space > > from page-flags-layout, we do try and fit a bunch of other crap in > > there, and at some point that all will not fit anymore and we'll revert > > to worse. > > > > I've no idea how far away from that we are for distro kernels. I suppose > > they have fairly large NR_NODES and NR_CPUS. > > I know it's not fashionable to care about them anymore, but it's sad if > 32-bit architectures miss out fundamental optimisations like this because > we're out of page flags. It would also be sad to increase the size of > struct page because we're too lazy to reduce flags. There's some that > might be able to be removed. I'm all for cleaning some of that up, but its been a long while since I poked in that general area. -- 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>