On Thu, 1 Mar 2018 08:17:50 +0100 Martin Schwidefsky <schwidef...@de.ibm.com> wrote:
> On Wed, 28 Feb 2018 14:31:53 -0800 > Matthew Wilcox <wi...@infradead.org> wrote: > > > From: Matthew Wilcox <mawil...@microsoft.com> > > > > I want to use the _mapcount field to record what a page is in use as. > > This can help with debugging and we can also expose that information to > > userspace through /proc/kpageflags to help diagnose memory usage (not > > included as part of this patch set). > > > > First, we need s390 to stop using _mapcount for its own purposes; > > Martin, I hope you have time to look at this patch. I must confess I > > don't quite understand what the different bits are used for in the upper > > nybble of the _mapcount, but I tried to replicate what you were doing > > faithfully. > > Yeah, that is a nasty bit of code. On s390 we have 2K page tables (pte) > but 4K pages. If we use full pages for the pte tables we waste 2K of > memory for each of the tables. So we allocate 4K and split it into two > 2K pieces. Now we have to keep track of the pieces to be able to free > them again. > > I try to give your patch a spin today. It should be stand-alone, no ? Ok, that seems to work just fine. System boots and survived some stress without loosing memory. Acked-by: Martin Schwidefsky <schwidef...@de.ibm.com> -- blue skies, Martin. "Reality continues to ruin my life." - Calvin.
