Messages in this thread Patch in this message | | | Date | Wed, 26 Mar 2008 10:55:00 -0700 | From | Suresh Siddha <> | Subject | Re: [Bug 10328] New: [regression] performance drop for glx |
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On Wed, Mar 26, 2008 at 06:29:11AM +0100, Ingo Molnar wrote: > > * Suresh Siddha <suresh.b.siddha@intel.com> wrote: > > > 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. > > thanks Suresh, applied.
Well, we need to take care of set_memory_uc() aswell, as the previous version didn't fix Alexey's issue.
Alexey, can you please test and ack this, before Andrew/Ingo can push relevant bits to their trees. Thanks. ---
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 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> Cc: Alexey Fisher <bug-track@fisher-privat.net> Cc: Ingo Molnar <mingo@elte.hu> Cc: Thomas Gleixner <tglx@linutronix.de> ---
diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c index 4afaba0..794895c 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 14e48b5..7b79f6b 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); diff --git a/include/asm-x86/pgtable.h b/include/asm-x86/pgtable.h index 174b877..9cf472a 100644 --- a/include/asm-x86/pgtable.h +++ b/include/asm-x86/pgtable.h @@ -85,6 +85,7 @@ extern pteval_t __PAGE_KERNEL, __PAGE_KERNEL_EXEC; #define __PAGE_KERNEL_RX (__PAGE_KERNEL_EXEC & ~_PAGE_RW) #define __PAGE_KERNEL_EXEC_NOCACHE (__PAGE_KERNEL_EXEC | _PAGE_PCD | _PAGE_PWT) #define __PAGE_KERNEL_NOCACHE (__PAGE_KERNEL | _PAGE_PCD | _PAGE_PWT) +#define __PAGE_KERNEL_UC_MINUS (__PAGE_KERNEL | _PAGE_PCD) #define __PAGE_KERNEL_VSYSCALL (__PAGE_KERNEL_RX | _PAGE_USER) #define __PAGE_KERNEL_VSYSCALL_NOCACHE (__PAGE_KERNEL_VSYSCALL | _PAGE_PCD | _PAGE_PWT) #define __PAGE_KERNEL_LARGE (__PAGE_KERNEL | _PAGE_PSE) @@ -101,6 +102,7 @@ extern pteval_t __PAGE_KERNEL, __PAGE_KERNEL_EXEC; #define PAGE_KERNEL_EXEC MAKE_GLOBAL(__PAGE_KERNEL_EXEC) #define PAGE_KERNEL_RX MAKE_GLOBAL(__PAGE_KERNEL_RX) #define PAGE_KERNEL_NOCACHE MAKE_GLOBAL(__PAGE_KERNEL_NOCACHE) +#define PAGE_KERNEL_UC_MINUS MAKE_GLOBAL(__PAGE_KERNEL_UC_MINUS) #define PAGE_KERNEL_EXEC_NOCACHE MAKE_GLOBAL(__PAGE_KERNEL_EXEC_NOCACHE) #define PAGE_KERNEL_LARGE MAKE_GLOBAL(__PAGE_KERNEL_LARGE) #define PAGE_KERNEL_LARGE_EXEC MAKE_GLOBAL(__PAGE_KERNEL_LARGE_EXEC)
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