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Carsten Otte 9723198c21 #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>
 		2008-01-17 15:38:59 -08:00
..
Kconfig sparsemem: make SPARSEMEM_VMEMMAP selectable 2007-12-17 19:28:16 -08:00
Makefile memory unplug: page isolation 2007-10-16 09:43:02 -07:00
allocpercpu.c Slab allocators: Replace explicit zeroing with __GFP_ZERO 2007-07-17 10:23:02 -07:00
backing-dev.c mm/backing-dev.c: fix percpu_counter_destroy call bug in bdi_init 2007-12-05 09:21:18 -08:00
bootmem.c [PATCH] remove EXPORT_UNUSED_SYMBOL'ed symbols 2006-12-07 08:39:44 -08:00
bounce.c block: Initial support for data-less (or empty) barrier support 2007-10-16 11:03:56 +02:00
fadvise.c [PATCH] mm: change uses of f_{dentry,vfsmnt} to use f_path 2006-12-08 08:28:43 -08:00
filemap.c Do dirty page accounting when removing a page from the page cache 2007-12-19 14:05:13 -08:00
filemap_xip.c xip: fix get_zeroed_page with __GFP_HIGHMEM 2008-01-08 16:10:36 -08:00
fremap.c remap_file_pages: kernel-doc corrections 2007-10-17 08:43:07 -07:00
highmem.c Create the ZONE_MOVABLE zone 2007-07-17 10:22:59 -07:00
hugetlb.c hugetlbfs: fix quota leak 2008-01-14 08:52:23 -08:00
internal.h Breakout page_order() to internal.h to avoid special knowledge of the buddy allocator 2007-10-16 09:43:01 -07:00
madvise.c speed up madvise_need_mmap_write() usage 2007-07-16 09:05:36 -07:00
memory.c #ifdef very expensive debug check in page fault path 2008-01-17 15:38:59 -08:00
memory_hotplug.c Add IORESOUCE_BUSY flag for System RAM 2007-11-14 18:45:39 -08:00
mempolicy.c Migration: find correct vma in new_vma_page() 2007-11-14 18:45:38 -08:00
mempool.c spelling fixes: mm/ 2007-10-20 01:27:18 +02:00
migrate.c Typo fixes retrun -> return 2007-10-20 02:13:26 +02:00
mincore.c [PATCH] mincore: vma crossing fix 2007-02-15 09:57:03 -08:00
mlock.c do not limit locked memory when RLIMIT_MEMLOCK is RLIM_INFINITY 2007-07-16 09:05:37 -07:00
mmap.c VM/Security: add security hook to do_brk 2007-12-05 09:21:21 -08:00
mmzone.c [PATCH] remove EXPORT_UNUSED_SYMBOL'ed symbols 2006-12-07 08:39:44 -08:00
mprotect.c fix mprotect vma_wants_writenotify prot 2007-10-23 08:32:06 -07:00
mremap.c sparse pointer use of zero as null 2007-10-18 14:37:31 -07:00
msync.c Detach sched.h from mm.h 2007-05-21 09:18:19 -07:00
nommu.c Security: round mmap hint address above mmap_min_addr 2007-12-06 00:25:10 +11:00
oom_kill.c oom_kill bug 2007-10-20 15:04:06 -07:00
page-writeback.c Revert "writeback: introduce writeback_control.more_io to indicate more io" 2008-01-14 21:21:29 -08:00
page_alloc.c mm: fix section mismatch warning in page_alloc.c 2008-01-17 15:38:58 -08:00
page_io.c Drop 'size' argument from bio_endio and bi_end_io 2007-10-10 09:25:57 +02:00
page_isolation.c memory hotremove: unset migrate type "ISOLATE" after removal 2007-11-14 18:45:38 -08:00
pdflush.c Freezer: make kernel threads nonfreezable by default 2007-07-17 10:23:02 -07:00
prio_tree.c spelling fixes: mm/ 2007-10-20 01:27:18 +02:00
quicklist.c quicklists: Only consider memory that can be used with GFP_KERNEL 2008-01-14 08:52:22 -08:00
readahead.c mm: bdi init hooks 2007-10-17 08:42:45 -07:00
rmap.c [S390] Optimize storage key handling for anonymous pages 2007-11-20 11:13:46 +01:00
shmem.c tmpfs: restore missing clear_highpage 2007-11-28 11:04:28 -08:00
shmem_acl.c [PATCH] Fix typos in mm/shmem_acl.c 2006-10-11 11:14:23 -07:00
slab.c Unify /proc/slabinfo configuration 2008-01-02 13:04:48 -08:00
slob.c Avoid double memclear() in SLOB/SLUB 2007-12-09 10:17:52 -08:00
slub.c Unify /proc/slabinfo configuration 2008-01-02 13:04:48 -08:00
sparse-vmemmap.c memory hotplug fix: fix section mismatch in vmammap_allock_block() 2007-11-29 09:24:54 -08:00
sparse.c mm/sparse.c: improve the error handling for sparse_add_one_section() 2007-12-17 19:28:16 -08:00
swap.c spelling fixes: mm/ 2007-10-20 01:27:18 +02:00
swap_state.c mm: clarify __add_to_swap_cache locking 2007-10-16 09:42:53 -07:00
swapfile.c Replace CONFIG_SOFTWARE_SUSPEND with CONFIG_HIBERNATION 2007-07-29 16:45:38 -07:00
thrash.c Bug in mm/thrash.c function grab_swap_token() 2007-05-11 08:29:32 -07:00
tiny-shmem.c r/o bind mounts: filesystem helpers for custom 'struct file's 2007-10-17 08:43:04 -07:00
truncate.c Drop some headers from mm.h 2007-10-17 08:42:55 -07:00
util.c fix mm/util.c:krealloc() 2007-11-14 18:45:41 -08:00
vmalloc.c spelling fixes: mm/ 2007-10-20 01:27:18 +02:00
vmscan.c spelling fixes: mm/ 2007-10-20 01:27:18 +02:00
vmstat.c vmstat: fix section mismatch warning 2007-11-14 18:45:42 -08:00