Gitweb:
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=9723198c219f3546982cb469e5aed26e68399055
Commit: 9723198c219f3546982cb469e5aed26e68399055
Parent: 6b2d2cec1081a979e0efd6a1e9559e5a01a3c10e
Author: Carsten Otte <[EMAIL PROTECTED]>
AuthorDate: Thu Jan 17 15:21:17 2008 -0800
Committer: Linus Torvalds <[EMAIL PROTECTED]>
CommitDate: Thu Jan 17 15:38:59 2008 -0800
#ifdef very expensive debug check in page fault path
This patch puts #ifdef CONFIG_DEBUG_VM around a check in vm_normal_page
that verifies that a pfn is valid. This patch increases performance of the
page fault microbenchmark in lmbench by 13% and overall dbench performance
by 7% on s390x. pfn_valid() is an expensive operation on s390 that needs a
high double digit amount of CPU cycles. Nick Piggin suggested that
pfn_valid() involves an array lookup on systems with sparsemem, and
therefore is an expensive operation there too.
The check looks like a clear debug thing to me, it should never trigger on
regular kernels. And if a pte is created for an invalid pfn, we'll find
out once the memory gets accessed later on anyway. Please consider
inclusion of this patch into mm.
Signed-off-by: Carsten Otte <[EMAIL PROTECTED]>
Acked-by: Nick Piggin <[EMAIL PROTECTED]>
Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
Signed-off-by: Linus Torvalds <[EMAIL PROTECTED]>
---
mm/memory.c | 2 ++
1 files changed, 2 insertions(+), 0 deletions(-)
diff --git a/mm/memory.c b/mm/memory.c
index 4bf0b6d..6dd1cd8 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -392,6 +392,7 @@ struct page *vm_normal_page(struct vm_area_struct *vma,
unsigned long addr, pte_
return NULL;
}
+#ifdef CONFIG_DEBUG_VM
/*
* Add some anal sanity checks for now. Eventually,
* we should just do "return pfn_to_page(pfn)", but
@@ -402,6 +403,7 @@ struct page *vm_normal_page(struct vm_area_struct *vma,
unsigned long addr, pte_
print_bad_pte(vma, pte, addr);
return NULL;
}
+#endif
/*
* NOTE! We still have PageReserved() pages in the page
-
To unsubscribe from this list: send the line "unsubscribe git-commits-head" in
the body of a message to [EMAIL PROTECTED]
More majordomo info at http://vger.kernel.org/majordomo-info.html
