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authorSuresh Siddha <suresh.b.siddha@intel.com>2008-03-26 03:39:12 +0300
committerIngo Molnar <mingo@elte.hu>2008-03-27 00:23:41 +0300
commitd546b67a940eb42a99f56b86c5cd8d47c8348c2a (patch)
tree5382b2d1800756aedad0a25643081de2eec6a4bf /arch
parent76c324182bbd29dfe4298ca65efb15be18055df1 (diff)
downloadlinux-d546b67a940eb42a99f56b86c5cd8d47c8348c2a.tar.xz
x86: fix performance drop for glx
fix the 3D performance drop reported at: http://bugzilla.kernel.org/show_bug.cgi?id=10328 fb drivers are using ioremap()/ioremap_nocache(), followed by mtrr_add with WC attribute. Recent changes in page attribute code made both ioremap()/ioremap_nocache() mappings as UC (instead of previous UC-). This breaks the graphics performance, as the effective memory type is UC instead of expected WC. The correct way to fix this is to add ioremap_wc() (which uses UC- in the absence of PAT kernel support and WC with PAT) and change all the fb drivers to use this new ioremap_wc() API. We can take this correct and longer route for post 2.6.25. For now, revert back to the UC- behavior for ioremap/ioremap_nocache. Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com> Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com> Cc: Arjan van de Ven <arjan@linux.intel.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/mm/ioremap.c6
-rw-r--r--arch/x86/mm/pageattr.c2
2 files changed, 6 insertions, 2 deletions
diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
index 4afaba0ed722..794895c6dcc9 100644
--- a/arch/x86/mm/ioremap.c
+++ b/arch/x86/mm/ioremap.c
@@ -137,7 +137,11 @@ static void __iomem *__ioremap(resource_size_t phys_addr, unsigned long size,
switch (mode) {
case IOR_MODE_UNCACHED:
default:
- prot = PAGE_KERNEL_NOCACHE;
+ /*
+ * FIXME: we will use UC MINUS for now, as video fb drivers
+ * depend on it. Upcoming ioremap_wc() will fix this behavior.
+ */
+ prot = PAGE_KERNEL_UC_MINUS;
break;
case IOR_MODE_CACHED:
prot = PAGE_KERNEL;
diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index 14e48b5a94ba..7b79f6be4e7d 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -771,7 +771,7 @@ static inline int change_page_attr_clear(unsigned long addr, int numpages,
int set_memory_uc(unsigned long addr, int numpages)
{
return change_page_attr_set(addr, numpages,
- __pgprot(_PAGE_PCD | _PAGE_PWT));
+ __pgprot(_PAGE_PCD));
}
EXPORT_SYMBOL(set_memory_uc);