Hi David, On Fri, 2018-11-09 at 10:04 +1000, David Airlie wrote: > On Thu, Nov 8, 2018 at 10:05 PM Jean Delvare <jdelv...@suse.de> wrote: > > > > On Thu, 1 Nov 2018 16:27:07 +0100, Jean Delvare wrote: > > > Hi David, > > > > > > The following commit: > > > > > > commit 7cf321d118a825c1541b43ca45294126fd474efa > > > Author: Dave Airlie > > > Date: Mon Oct 24 15:37:48 2016 +1000 > > > > > > drm/drivers: add support for using the arch wc mapping API. > > > > > > is causing a huge performance regression for the ast drm driver. In a > > > text console, if I call "cat" on a large text file, it takes almost > > > twice as much time to be displayed and scrolled completely. > > > > > > Can you please check that the ast driver portion of that commit is both > > > correct and complete? > > > > And in the meantime, what bad will happen if we just revert the ast > > portion of that commit? > > This seems likely to be a hw problem with PCI writes to the AST "GPU", > since it's just some sort of RAM + ARM on the end of a PCIE bus, we've > definitely seen possible issues in the past with write combining > around some of the mga GPUs with some CPUs.
Takashi asked me to compare the contents of /sys/kernel/debug/x86/pat_memtype_list before and after the commit above. Before the commit, we have: uncached-minus @ 0xfafe0000-0xfb000000 uncached-minus @ 0xfb000000-0xfb005000 write-combining @ 0xfb005000-0xfb584000 After the commit, we have: uncached-minus @ 0xfafe0000-0xfb000000 uncached-minus @ 0xfb000000-0xfb005000 uncached-minus @ 0xfb000000-0xfb800000 uncached-minus @ 0xfb005000-0xfb584000 The corresponding lines in /proc/iomem are: f0000000-fed8ffff : PCI Bus 0000:00 faf00000-fb7fffff : PCI Bus 0000:01 fafe0000-faffffff : 0000:01:01.0 fb000000-fb7fffff : 0000:01:01.0 Does it help? Is the change of type expected? Is it not a problem that one of the ranges is overlapping with 2 other ranges? -- Jean Delvare SUSE L3 Support _______________________________________________ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
