From de33c442ed2a465d2d7804b26dafd2eec067aa34 Mon Sep 17 00:00:00 2001 From: Suresh Siddha Date: Fri, 25 Apr 2008 17:07:22 -0700 Subject: x86 PAT: fix performance drop for glx, use UC minus for ioremap(), ioremap_nocache() and pci_mmap_page_range() 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 Signed-off-by: Venkatesh Pallipadi Signed-off-by: Ingo Molnar Signed-off-by: Thomas Gleixner --- arch/x86/mm/pageattr.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) (limited to 'arch/x86/mm/pageattr.c') diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c index bd5e05c654dc..60bcb5b6a37e 100644 --- a/arch/x86/mm/pageattr.c +++ b/arch/x86/mm/pageattr.c @@ -777,14 +777,20 @@ static inline int change_page_attr_clear(unsigned long addr, int numpages, int _set_memory_uc(unsigned long addr, int numpages) { + /* + * for now UC MINUS. see comments in ioremap_nocache() + */ return change_page_attr_set(addr, numpages, - __pgprot(_PAGE_CACHE_UC)); + __pgprot(_PAGE_CACHE_UC_MINUS)); } int set_memory_uc(unsigned long addr, int numpages) { + /* + * for now UC MINUS. see comments in ioremap_nocache() + */ if (reserve_memtype(addr, addr + numpages * PAGE_SIZE, - _PAGE_CACHE_UC, NULL)) + _PAGE_CACHE_UC_MINUS, NULL)) return -EINVAL; return _set_memory_uc(addr, numpages); -- cgit v1.2.1