summaryrefslogtreecommitdiff
path: root/mm/rmap.c
diff options
context:
space:
mode:
authorCarsten Otte <cotte@de.ibm.com>2008-01-17 23:21:17 (GMT)
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2008-01-17 23:38:59 (GMT)
commit9723198c219f3546982cb469e5aed26e68399055 (patch)
treeb8e195cb1ca1bdf143e4e564fdb43f09aadfd6f3 /mm/rmap.c
parent6b2d2cec1081a979e0efd6a1e9559e5a01a3c10e (diff)
downloadlinux-9723198c219f3546982cb469e5aed26e68399055.tar.xz
#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 <cotte@de.ibm.com> Acked-by: Nick Piggin <nickpiggin@yahoo.com.au> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/rmap.c')
0 files changed, 0 insertions, 0 deletions