x86 PAT: fix performance drop for glx, use UC minus for ioremap(), ioremap_nocache() and pci_mmap_page_range()

Browse source

Use UC_MINUS for ioremap(), ioremap_nocache() instead of strong UC.
Once all the X drivers move to ioremap_wc(), we can go back to strong
UC semantics for ioremap() and ioremap_nocache().

To avoid attribute aliasing issues, pci_mmap_page_range() will also
use UC_MINUS for default non write-combining mapping request.

Next steps:
	a) change all the video drivers using ioremap() or ioremap_nocache()
	   and adding WC MTTR using mttr_add() to ioremap_wc()

	b) for strict usage, we can go back to strong uc semantics
	   for ioremap() and ioremap_nocache() after some grace period for
	   completing step-a.

	c) user level X server needs to use the appropriate method for setting
	   up WC mapping (like using resourceX_wc sysfs file instead of
	   adding MTRR for WC and using /dev/mem or resourceX under /sys)

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

...

This commit is contained in:

Suresh Siddha 2008-04-25 17:07:22 -07:00 • committed by Ingo Molnar

parent b9b39bfba5

commit de33c442ed

3 changed files with 33 additions and 9 deletions

Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL

Download patch file Download diff file Expand all files Collapse all files

20

arch/x86/mm/ioremap.c

View file

10

arch/x86/mm/pageattr.c

View file

12

arch/x86/pci/i386.c

View file