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[PATCH v2 0/3] Optimize CONFIG_DEBUG_PAGEALLOC

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  [PATCH v2 0/3] Optimize CONFIG_DEBUG_PAGEALLOC Christian Borntraeger <borntraeger@de.ibm.com> - 2016-01-27 10:00 +0100
    [PATCH v2 1/3] mm: provide debug_pagealloc_enabled() without CONFIG_DEBUG_PAGEALLOC Christian Borntraeger <borntraeger@de.ibm.com> - 2016-01-27 10:00 +0100
      Re: [PATCH v2 1/3] mm: provide debug_pagealloc_enabled() without  CONFIG_DEBUG_PAGEALLOC Thomas Gleixner <tglx@linutronix.de> - 2016-01-27 10:20 +0100

#1318762 — [PATCH v2 0/3] Optimize CONFIG_DEBUG_PAGEALLOC

As CONFIG_DEBUG_PAGEALLOC can be enabled/disabled via kernel
parameters we can optimize some cases by checking the enablement
state.

I have done s390 and x86 as examples.
s390 should be ok, I tested several combinations, x86 seems to
work as well, but I have some concerns about the 1GB pages.
The previous code did not bother at all with CONFIG_DEBUG_PAGEALLOC
and I do not fully understand why.

Power can probably do the same, Michael/Ben?
I am not sure about sparc. Sparc seems to allocate the TSB buffer
really early. David?


V1->V2:
- replace DEBUG_PAGEALLOC(disabled/enabled) with DEBUG_PAGEALLOC
  dump_stack for s390/x86
- add /* CONFIG_DEBUG_PAGEALLOC */ to else and endif


Christian Borntraeger (3):
  mm: provide debug_pagealloc_enabled() without CONFIG_DEBUG_PAGEALLOC
  x86: query dynamic DEBUG_PAGEALLOC setting
  s390: query dynamic DEBUG_PAGEALLOC setting

 arch/s390/kernel/dumpstack.c |  8 ++++----
 arch/s390/mm/vmem.c          | 10 ++++------
 arch/x86/kernel/dumpstack.c  |  5 ++---
 arch/x86/mm/init.c           |  7 ++++---
 arch/x86/mm/pageattr.c       | 14 ++++----------
 include/linux/mm.h           |  9 +++++++--
 6 files changed, 25 insertions(+), 28 deletions(-)

-- 
2.3.0

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#1318763 — [PATCH v2 1/3] mm: provide debug_pagealloc_enabled() without CONFIG_DEBUG_PAGEALLOC

We can provide debug_pagealloc_enabled() also if CONFIG_DEBUG_PAGEALLOC
is not set. It will return false in that case.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Acked-by: David Rientjes <rientjes@google.com>
---
 include/linux/mm.h | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 7783073..56cab4e 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2147,13 +2147,18 @@ kernel_map_pages(struct page *page, int numpages, int enable)
 #ifdef CONFIG_HIBERNATION
 extern bool kernel_page_present(struct page *page);
 #endif /* CONFIG_HIBERNATION */
-#else
+#else  /* CONFIG_DEBUG_PAGEALLOC */
+static inline bool debug_pagealloc_enabled(void)
+{
+	return false;
+}
+
 static inline void
 kernel_map_pages(struct page *page, int numpages, int enable) {}
 #ifdef CONFIG_HIBERNATION
 static inline bool kernel_page_present(struct page *page) { return true; }
 #endif /* CONFIG_HIBERNATION */
-#endif
+#endif /* CONFIG_DEBUG_PAGEALLOC */
 
 #ifdef __HAVE_ARCH_GATE_AREA
 extern struct vm_area_struct *get_gate_vma(struct mm_struct *mm);
-- 
2.3.0

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#1318767 — Re: [PATCH v2 1/3] mm: provide debug_pagealloc_enabled() without CONFIG_DEBUG_PAGEALLOC

On Wed, 27 Jan 2016, Christian Borntraeger wrote:

> We can provide debug_pagealloc_enabled() also if CONFIG_DEBUG_PAGEALLOC
> is not set. It will return false in that case.
> 
> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
> Acked-by: David Rientjes <rientjes@google.com>

Acked-by: Thomas Gleixner <tglx@linutronix.de>

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