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Date: Mon, 28 Apr 2008 18:34:57 +0200
From: Ingo Molnar <mingo@...e.hu>
To: Suresh Siddha <suresh.b.siddha@...el.com>
Cc: Alexey Fisher <bug-track@...her-privat.net>,
Arjan van de Ven <arjan@...ux.intel.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Thomas Gleixner <tglx@...utronix.de>,
bugme-daemon@...zilla.kernel.org, linux-kernel@...r.kernel.org,
"Rafael J. Wysocki" <rjw@...k.pl>, venkatesh.pallipadi@...el.com,
jbarnes@...tuousgeek.org, keithp@...thp.com, airlied@...il.com
Subject: Re: [Bug 10328] New: [regression] performance drop for glx
* Suresh Siddha <suresh.b.siddha@...el.com> wrote:
> Alexey, Sorry. I missed posting a fix in the post PAT series for this
> issue. Can you please try the appended patch and Ack?
>
> copying X folks get their attention and their Ack on the patch and
> next steps outlined.
i queued up the patch below - hand-merged to x86.git.
Ingo
----------->
Subject: x86 PAT: fix performance drop for glx, use UC minus for ioremap(), ioremap_nocache() and pci_mmap_page_range()
From: Suresh Siddha <suresh.b.siddha@...el.com>
Date: Fri, 25 Apr 2008 17:07:22 -0700
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@...el.com>
Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@...el.com>
Signed-off-by: Ingo Molnar <mingo@...e.hu>
---
arch/x86/mm/ioremap.c | 20 ++++++++++++++++----
arch/x86/mm/pageattr.c | 10 ++++++++--
arch/x86/pci/i386.c | 12 +++++++++---
3 files changed, 33 insertions(+), 9 deletions(-)
Index: linux-x86.q/arch/x86/mm/ioremap.c
===================================================================
--- linux-x86.q.orig/arch/x86/mm/ioremap.c
+++ linux-x86.q/arch/x86/mm/ioremap.c
@@ -176,11 +176,11 @@ static void __iomem *__ioremap(resource_
/*
* Do not fallback to certain memory types with certain
* requested type:
- * - request is uncached, return cannot be write-back
- * - request is uncached, return cannot be write-combine
+ * - request is uc-, return cannot be write-back
+ * - request is uc-, return cannot be write-combine
* - request is write-combine, return cannot be write-back
*/
- if ((prot_val == _PAGE_CACHE_UC &&
+ if ((prot_val == _PAGE_CACHE_UC_MINUS &&
(new_prot_val == _PAGE_CACHE_WB ||
new_prot_val == _PAGE_CACHE_WC)) ||
(prot_val == _PAGE_CACHE_WC &&
@@ -201,6 +201,9 @@ static void __iomem *__ioremap(resource_
default:
prot = PAGE_KERNEL_NOCACHE;
break;
+ case _PAGE_CACHE_UC_MINUS:
+ prot = PAGE_KERNEL_UC_MINUS;
+ break;
case _PAGE_CACHE_WC:
prot = PAGE_KERNEL_WC;
break;
@@ -255,7 +258,16 @@ static void __iomem *__ioremap(resource_
*/
void __iomem *ioremap_nocache(resource_size_t phys_addr, unsigned long size)
{
- return __ioremap(phys_addr, size, _PAGE_CACHE_UC);
+ /*
+ * Ideally, this should be:
+ * pat_wc_enabled ? _PAGE_CACHE_UC : _PAGE_CACHE_UC_MINUS;
+ *
+ * Till we fix all X drivers to use ioremap_wc(), we will use
+ * UC MINUS.
+ */
+ unsigned long val = _PAGE_CACHE_UC_MINUS;
+
+ return __ioremap(phys_addr, size, val);
}
EXPORT_SYMBOL(ioremap_nocache);
Index: linux-x86.q/arch/x86/mm/pageattr.c
===================================================================
--- linux-x86.q.orig/arch/x86/mm/pageattr.c
+++ linux-x86.q/arch/x86/mm/pageattr.c
@@ -829,14 +829,20 @@ static inline int change_page_attr_clear
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), 0);
+ __pgprot(_PAGE_CACHE_UC_MINUS), 0);
}
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);
Index: linux-x86.q/arch/x86/pci/i386.c
===================================================================
--- linux-x86.q.orig/arch/x86/pci/i386.c
+++ linux-x86.q/arch/x86/pci/i386.c
@@ -301,6 +301,13 @@ int pci_mmap_page_range(struct pci_dev *
prot = pgprot_val(vma->vm_page_prot);
if (pat_wc_enabled && write_combine)
prot |= _PAGE_CACHE_WC;
+ else if (pat_wc_enabled)
+ /*
+ * ioremap() and ioremap_nocache() defaults to UC MINUS for now.
+ * To avoid attribute conflicts, request UC MINUS here
+ * aswell.
+ */
+ prot |= _PAGE_CACHE_UC_MINUS;
else if (boot_cpu_data.x86 > 3)
prot |= _PAGE_CACHE_UC;
@@ -319,9 +326,8 @@ int pci_mmap_page_range(struct pci_dev *
* - request is uncached, return cannot be write-combine
* - request is write-combine, return cannot be write-back
*/
- if ((flags == _PAGE_CACHE_UC &&
- (new_flags == _PAGE_CACHE_WB ||
- new_flags == _PAGE_CACHE_WC)) ||
+ if ((flags == _PAGE_CACHE_UC_MINUS &&
+ (new_flags == _PAGE_CACHE_WB)) ||
(flags == _PAGE_CACHE_WC &&
new_flags == _PAGE_CACHE_WB)) {
free_memtype(addr, addr+len);
--
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