Quite a bit of code is used in maintaining these "cached pages" that are
probably pretty unlikely to get used. It would require a narrow race where
the page is inserted concurrently while this process is allocating a page
in order to create the spare page. Then a multi-page write into an uncached
part of the file, to make use of it.

Next, the buffered write path (and others) uses its own LRU pagevec when it
should be just using the per-CPU LRU pagevec (which will cut down on both data
and code size cacheline footprint). Also, these private LRU pagevecs are
emptied after just a very short time, in contrast with the per-CPU pagevecs
that are persistent. Net result: 7.3 times fewer lru_lock acquisitions required
to add the pages to pagecache for a bulk write (in 4K chunks).

[this gets rid of some cond_resched() calls in readahead.c and mpage.c due
 to clashes in -mm. What put them there, and why? ]
Signed-off-by: NNick Piggin <npiggin@suse.de>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

If prepare_write fails with AOP_TRUNCATED_PAGE, or if commit_write fails, then
we may have failed the write operation despite prepare_write having
instantiated blocks past i_size.  Fix this, and consolidate the trimming into
one place.
Signed-off-by: NNick Piggin <npiggin@suse.de>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Allow CONFIG_DEBUG_VM to switch off the prefaulting logic, to simulate the
Makes the race much easier to hit.

This is useful for demonstration and testing purposes, but is removed in a
subsequent patch.
Signed-off-by: NNick Piggin <npiggin@suse.de>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Rename some variables and fix some types.
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NNick Piggin <npiggin@suse.de>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This reverts commit 6527c2bd, which
fixed the following bug:

  When prefaulting in the pages in generic_file_buffered_write(), we only
  faulted in the pages for the firts segment of the iovec.  If the second of
  successive segment described a mmapping of the page into which we're
  write()ing, and that page is not up-to-date, the fault handler tries to lock
  the already-locked page (to bring it up to date) and deadlocks.

  An exploit for this bug is in writev-deadlock-demo.c, in
  http://www.zip.com.au/~akpm/linux/patches/stuff/ext3-tools.tar.gz.

  (These demos assume blocksize < PAGE_CACHE_SIZE).

The problem with this fix is that it takes the kernel back to doing a single
prepare_write()/commit_write() per iovec segment.  So in the worst case we'll
run prepare_write+commit_write 1024 times where we previously would have run
it once. The other problem with the fix is that it fix all the locking problems.

<insert numbers obtained via ext3-tools's writev-speed.c here>

And apparently this change killed NFS overwrite performance, because, I
suppose, it talks to the server for each prepare_write+commit_write.

So just back that patch out - we'll be fixing the deadlock by other means.

Nick says: also it only ever actually papered over the bug, because after
faulting in the pages, they might be unmapped or reclaimed.
Signed-off-by: NNick Piggin <npiggin@suse.de>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This reverts commit 81b0c871, which was
a bugfix against 6527c2bd ("[PATCH]
generic_file_buffered_write(): deadlock on vectored write"), which we
also revert.
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NNick Piggin <npiggin@suse.de>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Revert the patch from Neil Brown to optimise NFSD writev handling.

Cc: Neil Brown <neilb@suse.de>
Signed-off-by: NNick Piggin <npiggin@suse.de>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

While running some memory intensive load, system response deteriorated just
after swap-out started.

The cause of this problem is that when a PG_reclaim page is moved to the tail
of the inactive LRU list in rotate_reclaimable_page(), lru_lock spin lock is
acquired every page writeback .  This deteriorates system performance and
makes interrupt hold off time longer when swap-out started.

Following patch solves this problem.  I use pagevec in rotating reclaimable
pages to mitigate LRU spin lock contention and reduce interrupt hold off time.

I did a test that allocating and touching pages in multiple processes, and
pinging to the test machine in flooding mode to measure response under memory
intensive load.

The test result is:

	-2.6.23-rc5
	--- testmachine ping statistics ---
	3000 packets transmitted, 3000 received, 0% packet loss, time 53222ms
	rtt min/avg/max/mdev = 0.074/0.652/172.228/7.176 ms, pipe 11, ipg/ewma
17.746/0.092 ms

	-2.6.23-rc5-patched
	--- testmachine ping statistics ---
	3000 packets transmitted, 3000 received, 0% packet loss, time 51924ms
	rtt min/avg/max/mdev = 0.072/0.108/3.884/0.114 ms, pipe 2, ipg/ewma
17.314/0.091 ms

Max round-trip-time was improved.

The test machine spec is that 4CPU(3.16GHz, Hyper-threading enabled)
8GB memory , 8GB swap.

I did ping test again to observe performance deterioration caused by taking
a ref.

	-2.6.23-rc6-with-modifiedpatch
	--- testmachine ping statistics ---
	3000 packets transmitted, 3000 received, 0% packet loss, time 53386ms
	rtt min/avg/max/mdev = 0.074/0.110/4.716/0.147 ms, pipe 2, ipg/ewma 17.801/0.129 ms

The result for my original patch is as follows.

	-2.6.23-rc5-with-originalpatch
	--- testmachine ping statistics ---
	3000 packets transmitted, 3000 received, 0% packet loss, time 51924ms
	rtt min/avg/max/mdev = 0.072/0.108/3.884/0.114 ms, pipe 2, ipg/ewma 17.314/0.091 ms

The influence to response was small.

[akpm@linux-foundation.org: fix uninitalised var warning]
[hugh@veritas.com: fix locking]
[randy.dunlap@oracle.com: fix function declaration]
[hugh@veritas.com: fix BUG at include/linux/mm.h:220!]
[hugh@veritas.com: kill redundancy in rotate_reclaimable_page]
[hugh@veritas.com: move_tail_pages into lru_add_drain]
Signed-off-by: NHisashi Hifumi <hifumi.hisashi@oss.ntt.co.jp>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Allow an application to query the memories allowed by its context.

Updated numa_memory_policy.txt to mention that applications can use this to
obtain allowed memories for constructing valid policies.

TODO:  update out-of-tree libnuma wrapper[s], or maybe add a new
wrapper--e.g.,  numa_get_mems_allowed() ?

Also, update numa syscall man pages.

Tested with memtoy V>=0.13.
Signed-off-by: NLee Schermerhorn <lee.schermerhorn@hp.com>
Acked-by: NChristoph Lameter <clameter@sgi.com>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The current VM can get itself into trouble fairly easily on systems with a
small ZONE_HIGHMEM, which is common on i686 computers with 1GB of memory.

On one side, page_alloc() will allocate down to zone->pages_low, while on
the other side, kswapd() and balance_pgdat() will try to free memory from
every zone, until every zone has more free pages than zone->pages_high.

Highmem can be filled up to zone->pages_low with page tables, ramfs,
vmalloc allocations and other unswappable things quite easily and without
many bad side effects, since we still have a huge ZONE_NORMAL to do future
allocations from.

However, as long as the number of free pages in the highmem zone is below
zone->pages_high, kswapd will continue swapping things out from
ZONE_NORMAL, too!

Sami Farin managed to get his system into a stage where kswapd had freed
about 700MB of low memory and was still "going strong".

The attached patch will make kswapd stop paging out data from zones when
there is more than enough memory free.  We do go above zone->pages_high in
order to keep pressure between zones equal in normal circumstances, but the
patch should prevent the kind of excesses that made Sami's computer totally
unusable.
Signed-off-by: NRik van Riel <riel@redhat.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

vmalloc() returns a void pointer, so there's no need to cast its
return value in mm/page_alloc.c::zone_wait_table_init().
Signed-off-by: NJesper Juhl <jesper.juhl@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

A NULL pointer means that the object was not allocated.  One cannot
determine the size of an object that has not been allocated.  Currently we
return 0 but we really should BUG() on attempts to determine the size of
something nonexistent.

krealloc() interprets NULL to mean a zero sized object.  Handle that
separately in krealloc().
Signed-off-by: NChristoph Lameter <clameter@sgi.com>
Acked-by: NPekka Enberg <penberg@cs.helsinki.fi>
Cc: Matt Mackall <mpm@selenic.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The calculation of pgoff in do_linear_fault() should use PAGE_SHIFT and not
PAGE_CACHE_SHIFT since vma->vm_pgoff is in units of PAGE_SIZE and not
PAGE_CACHE_SIZE.  At the moment linux/pagemap.h has PAGE_CACHE_SHIFT
defined as PAGE_SHIFT, but should that ever change this calculation would
break.
Signed-off-by: NDean Nelson <dcn@sgi.com>
Acked-by: NNick Piggin <npiggin@suse.de>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Considering kfree(NULL) would normally occur only in error paths and
kfree(ZERO_SIZE_PTR) is uncommon as well, so let's use unlikely() for the
condition check in SLUB's and SLOB's kfree() to optimize for the common
case.  SLAB has this already.
Signed-off-by: NSatyam Sharma <satyam@infradead.org>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Christoph Lameter <clameter@sgi.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

__add_to_swap_cache unconditionally sets the page locked, which can be a bit
alarming to the unsuspecting reader: in the code paths where the page is
visible to other CPUs, the page should be (and is) already locked.

Instead, just add a check to ensure the page is locked here, and teach the one
path relying on the old behaviour to call SetPageLocked itself.

[hugh@veritas.com: locking fix]
Signed-off-by: NNick Piggin <npiggin@suse.de>
Signed-off-by: NHugh Dickins <hugh@veritas.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

find_lock_page does not need to recheck ->index because if the page is in the
right mapping then the index must be the same.  Also, tree_lock does not need
to be retaken after the page is locked in order to test that ->mapping has not
changed, because holding the page lock pins its mapping.
Signed-off-by: NNick Piggin <npiggin@suse.de>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Probing pages and radix_tree_tagged are lockless operations with the lockless
radix-tree.  Convert these users to RCU locking rather than using tree_lock.
Signed-off-by: NNick Piggin <npiggin@suse.de>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The commit b5810039 contains the note

  A last caveat: the ZERO_PAGE is now refcounted and managed with rmap
  (and thus mapcounted and count towards shared rss).  These writes to
  the struct page could cause excessive cacheline bouncing on big
  systems.  There are a number of ways this could be addressed if it is
  an issue.

And indeed this cacheline bouncing has shown up on large SGI systems.
There was a situation where an Altix system was essentially livelocked
tearing down ZERO_PAGE pagetables when an HPC app aborted during startup.
This situation can be avoided in userspace, but it does highlight the
potential scalability problem with refcounting ZERO_PAGE, and corner
cases where it can really hurt (we don't want the system to livelock!).

There are several broad ways to fix this problem:
1. add back some special casing to avoid refcounting ZERO_PAGE
2. per-node or per-cpu ZERO_PAGES
3. remove the ZERO_PAGE completely

I will argue for 3. The others should also fix the problem, but they
result in more complex code than does 3, with little or no real benefit
that I can see.

Why? Inserting a ZERO_PAGE for anonymous read faults appears to be a
false optimisation: if an application is performance critical, it would
not be doing many read faults of new memory, or at least it could be
expected to write to that memory soon afterwards. If cache or memory use
is critical, it should not be working with a significant number of
ZERO_PAGEs anyway (a more compact representation of zeroes should be
used).

As a sanity check -- mesuring on my desktop system, there are never many
mappings to the ZERO_PAGE (eg. 2 or 3), thus memory usage here should not
increase much without it.

When running a make -j4 kernel compile on my dual core system, there are
about 1,000 mappings to the ZERO_PAGE created per second, but about 1,000
ZERO_PAGE COW faults per second (less than 1 ZERO_PAGE mapping per second
is torn down without being COWed). So removing ZERO_PAGE will save 1,000
page faults per second when running kbuild, while keeping it only saves
less than 1 page clearing operation per second. 1 page clear is cheaper
than a thousand faults, presumably, so there isn't an obvious loss.

Neither the logical argument nor these basic tests give a guarantee of no
regressions. However, this is a reasonable opportunity to try to remove
the ZERO_PAGE from the pagefault path. If it is found to cause regressions,
we can reintroduce it and just avoid refcounting it.

The /dev/zero ZERO_PAGE usage and TLB tricks also get nuked.  I don't see
much use to them except on benchmarks.  All other users of ZERO_PAGE are
converted just to use ZERO_PAGE(0) for simplicity. We can look at
replacing them all and maybe ripping out ZERO_PAGE completely when we are
more satisfied with this solution.
Signed-off-by: NNick Piggin <npiggin@suse.de>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus "snif" Torvalds <torvalds@linux-foundation.org>

This gets rid of all kmalloc caches larger than page size.  A kmalloc
request larger than PAGE_SIZE > 2 is going to be passed through to the page
allocator.  This works both inline where we will call __get_free_pages
instead of kmem_cache_alloc and in __kmalloc.

kfree is modified to check if the object is in a slab page. If not then
the page is freed via the page allocator instead. Roughly similar to what
SLOB does.

Advantages:
- Reduces memory overhead for kmalloc array
- Large kmalloc operations are faster since they do not
  need to pass through the slab allocator to get to the
  page allocator.
- Performance increase of 10%-20% on alloc and 50% on free for
  PAGE_SIZEd allocations.
  SLUB must call page allocator for each alloc anyways since
  the higher order pages which that allowed avoiding the page alloc calls
  are not available in a reliable way anymore. So we are basically removing
  useless slab allocator overhead.
- Large kmallocs yields page aligned object which is what
  SLAB did. Bad things like using page sized kmalloc allocations to
  stand in for page allocate allocs can be transparently handled and are not
  distinguishable from page allocator uses.
- Checking for too large objects can be removed since
  it is done by the page allocator.

Drawbacks:
- No accounting for large kmalloc slab allocations anymore
- No debugging of large kmalloc slab allocations.
Signed-off-by: NChristoph Lameter <clameter@sgi.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Convert some 'unsigned long' to pgoff_t.
Signed-off-by: NFengguang Wu <wfg@mail.ustc.edu.cn>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

- remove unused local next_index in do_generic_mapping_read()
- remove a redudant page_cache_read() declaration
Signed-off-by: NFengguang Wu <wfg@mail.ustc.edu.cn>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Remove VM_MAX_CACHE_HIT, MAX_RA_PAGES and MIN_RA_PAGES.
Signed-off-by: NFengguang Wu <wfg@mail.ustc.edu.cn>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The local copy of ra in do_generic_mapping_read() can now go away.

It predates readanead(req_size).  In a time when the readahead code was called
on *every* single page.  Hence a local has to be made to reduce the chance of
the readahead state being overwritten by a concurrent reader.  More details
in: Linux: Random File I/O Regressions In 2.6
<http://kerneltrap.org/node/3039>

Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: NFengguang Wu <wfg@mail.ustc.edu.cn>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This is a simplified version of the pagecache context based readahead.  It
handles the case of multiple threads reading on the same fd and invalidating
each others' readahead state.  It does the trick by scanning the pagecache and
recovering the current read stream's readahead status.

The algorithm works in a opportunistic way, in that it does not try to detect
interleaved reads _actively_, which requires a probe into the page cache
(which means a little more overhead for random reads).  It only tries to
handle a previously started sequential readahead whose state was overwritten
by another concurrent stream, and it can do this job pretty well.

Negative and positive examples(or what you can expect from it):

1) it cannot detect and serve perfect request-by-request interleaved reads
   right:
	time	stream 1  stream 2
	0 	1
	1 	          1001
	2 	2
	3 	          1002
	4 	3
	5 	          1003
	6 	4
	7 	          1004
	8 	5
	9	          1005

Here no single readahead will be carried out.

2) However, if it's two concurrent reads by two threads, the chance of the
   initial sequential readahead be started is huge. Once the first sequential
   readahead is started for a stream, this patch will ensure that the readahead
   window continues to rampup and won't be disturbed by other streams.

	time	stream 1  stream 2
	0 	1
	1 	2
	2 	          1001
	3 	3
	4 	          1002
	5 	          1003
	6 	4
	7 	5
	8 	          1004
	9 	6
	10	          1005
	11	7
	12	          1006
	13	          1007

Here stream 1 will start a readahead at page 2, and stream 2 will start its
first readahead at page 1003.  From then on the two streams will be served
right.

Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: NFengguang Wu <wfg@mail.ustc.edu.cn>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Combine the file_ra_state members
				unsigned long prev_index
				unsigned int prev_offset
into
				loff_t prev_pos

It is more consistent and better supports huge files.

Thanks to Peter for the nice proposal!

[akpm@linux-foundation.org: fix shift overflow]
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: NFengguang Wu <wfg@mail.ustc.edu.cn>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Fold file_ra_state.mmap_hit into file_ra_state.mmap_miss and make it an int.
Signed-off-by: NFengguang Wu <wfg@mail.ustc.edu.cn>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Use 'unsigned int' instead of 'unsigned long' for readahead sizes.

This helps reduce memory consumption on 64bit CPU when a lot of files are
opened.

CC: Andi Kleen <andi@firstfloor.org>
Signed-off-by: NFengguang Wu <wfg@mail.ustc.edu.cn>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This patch cleans up duplicate includes in
	mm/
Signed-off-by: NJesper Juhl <jesper.juhl@gmail.com>
Acked-by: NPaul Mundt <lethal@linux-sh.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

WARNING: mm/built-in.o(.text+0x24bd3): Section mismatch: reference to .init.text:early_kmem_cache_node_alloc (between 'init_kmem_cache_nodes' and 'calculate_sizes')
...
Signed-off-by: NAdrian Bunk <bunk@stusta.de>
Acked-by: NChristoph Lameter <clameter@sgi.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Convert the common vmemmap population into initialisation helpers for use by
architecture vmemmap populators.  All architecture implementing the
SPARSEMEM_VMEMMAP variant supply an architecture specific vmemmap_populate()
initialiser, which may make use of the helpers.

This allows us to clean up and remove the initialisation Kconfig entries.
With this patch there is a single SPARSEMEM_VMEMMAP_ENABLE Kconfig option to
indicate use of that variant.
Signed-off-by: NAndy Whitcroft <apw@shadowen.org>
Acked-by: NChristoph Lameter <clameter@sgi.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

SPARSEMEM is a pretty nice framework that unifies quite a bit of code over all
the arches.  It would be great if it could be the default so that we can get
rid of various forms of DISCONTIG and other variations on memory maps.  So far
what has hindered this are the additional lookups that SPARSEMEM introduces
for virt_to_page and page_address.  This goes so far that the code to do this
has to be kept in a separate function and cannot be used inline.

This patch introduces a virtual memmap mode for SPARSEMEM, in which the memmap
is mapped into a virtually contigious area, only the active sections are
physically backed.  This allows virt_to_page page_address and cohorts become
simple shift/add operations.  No page flag fields, no table lookups, nothing
involving memory is required.

The two key operations pfn_to_page and page_to_page become:

   #define __pfn_to_page(pfn)      (vmemmap + (pfn))
   #define __page_to_pfn(page)     ((page) - vmemmap)

By having a virtual mapping for the memmap we allow simple access without
wasting physical memory.  As kernel memory is typically already mapped 1:1
this introduces no additional overhead.  The virtual mapping must be big
enough to allow a struct page to be allocated and mapped for all valid
physical pages.  This vill make a virtual memmap difficult to use on 32 bit
platforms that support 36 address bits.

However, if there is enough virtual space available and the arch already maps
its 1-1 kernel space using TLBs (f.e.  true of IA64 and x86_64) then this
technique makes SPARSEMEM lookups even more efficient than CONFIG_FLATMEM.
FLATMEM needs to read the contents of the mem_map variable to get the start of
the memmap and then add the offset to the required entry.  vmemmap is a
constant to which we can simply add the offset.

This patch has the potential to allow us to make SPARSMEM the default (and
even the only) option for most systems.  It should be optimal on UP, SMP and
NUMA on most platforms.  Then we may even be able to remove the other memory
models: FLATMEM, DISCONTIG etc.

[apw@shadowen.org: config cleanups, resplit code etc]
[kamezawa.hiroyu@jp.fujitsu.com: Fix sparsemem_vmemmap init]
[apw@shadowen.org: vmemmap: remove excess debugging]
[apw@shadowen.org: simplify initialisation code and reduce duplication]
[apw@shadowen.org: pull out the vmemmap code into its own file]
Signed-off-by: NChristoph Lameter <clameter@sgi.com>
Signed-off-by: NAndy Whitcroft <apw@shadowen.org>
Acked-by: NMel Gorman <mel@csn.ul.ie>
Cc: "Luck, Tony" <tony.luck@intel.com>
Cc: Andi Kleen <ak@suse.de>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

We have flags to indicate whether a section actually has a valid mem_map
associated with it.  This is never set and we rely solely on the present bit
to indicate a section is valid.  By definition a section is not valid if it
has no mem_map and there is a window during init where the present bit is set
but there is no mem_map, during which pfn_valid() will return true
incorrectly.

Use the existing SECTION_HAS_MEM_MAP flag to indicate the presence of a valid
mem_map.  Switch valid_section{,_nr} and pfn_valid() to this bit.  Add a new
present_section{,_nr} and pfn_present() interfaces for those users who care to
know that a section is going to be valid.

[akpm@linux-foundation.org: coding-syle fixes]
Signed-off-by: NAndy Whitcroft <apw@shadowen.org>
Acked-by: NMel Gorman <mel@csn.ul.ie>
Cc: Christoph Lameter <clameter@sgi.com>
Cc: "Luck, Tony" <tony.luck@intel.com>
Cc: Andi Kleen <ak@suse.de>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

SPARSEMEM is a pretty nice framework that unifies quite a bit of code over all
the arches.  It would be great if it could be the default so that we can get
rid of various forms of DISCONTIG and other variations on memory maps.  So far
what has hindered this are the additional lookups that SPARSEMEM introduces
for virt_to_page and page_address.  This goes so far that the code to do this
has to be kept in a separate function and cannot be used inline.

This patch introduces a virtual memmap mode for SPARSEMEM, in which the memmap
is mapped into a virtually contigious area, only the active sections are
physically backed.  This allows virt_to_page page_address and cohorts become
simple shift/add operations.  No page flag fields, no table lookups, nothing
involving memory is required.

The two key operations pfn_to_page and page_to_page become:

   #define __pfn_to_page(pfn)      (vmemmap + (pfn))
   #define __page_to_pfn(page)     ((page) - vmemmap)

By having a virtual mapping for the memmap we allow simple access without
wasting physical memory.  As kernel memory is typically already mapped 1:1
this introduces no additional overhead.  The virtual mapping must be big
enough to allow a struct page to be allocated and mapped for all valid
physical pages.  This vill make a virtual memmap difficult to use on 32 bit
platforms that support 36 address bits.

However, if there is enough virtual space available and the arch already maps
its 1-1 kernel space using TLBs (f.e.  true of IA64 and x86_64) then this
technique makes SPARSEMEM lookups even more efficient than CONFIG_FLATMEM.
FLATMEM needs to read the contents of the mem_map variable to get the start of
the memmap and then add the offset to the required entry.  vmemmap is a
constant to which we can simply add the offset.

This patch has the potential to allow us to make SPARSMEM the default (and
even the only) option for most systems.  It should be optimal on UP, SMP and
NUMA on most platforms.  Then we may even be able to remove the other memory
models: FLATMEM, DISCONTIG etc.

The current aim is to bring a common virtually mapped mem_map to all
architectures.  This should facilitate the removal of the bespoke
implementations from the architectures.  This also brings performance
improvements for most architecture making sparsmem vmemmap the more desirable
memory model.  The ultimate aim of this work is to expand sparsemem support to
encompass all the features of the other memory models.  This could allow us to
drop support for and remove the other models in the longer term.

Below are some comparitive kernbench numbers for various architectures,
comparing default memory model against SPARSEMEM VMEMMAP.  All but ia64 show
marginal improvement; we expect the ia64 figures to be sorted out when the
larger mapping support returns.

x86-64 non-NUMA
             Base    VMEMAP    % change (-ve good)
User        85.07     84.84    -0.26
System      34.32     33.84    -1.39
Total      119.38    118.68    -0.59

ia64
             Base    VMEMAP    % change (-ve good)
User      1016.41   1016.93    0.05
System      50.83     51.02    0.36
Total     1067.25   1067.95    0.07

x86-64 NUMA
             Base   VMEMAP    % change (-ve good)
User        30.77   431.73     0.22
System      45.39    43.98    -3.11
Total      476.17   475.71    -0.10

ppc64
             Base   VMEMAP    % change (-ve good)
User       488.77   488.35    -0.09
System      56.92    56.37    -0.97
Total      545.69   544.72    -0.18

Below are some AIM bencharks on IA64 and x86-64 (thank Bob).  The seems
pretty much flat as you would expect.

ia64 results 2 cpu non-numa 4Gb SCSI disk

Benchmark	Version	Machine	Run Date
AIM Multiuser Benchmark - Suite VII	"1.1"	extreme	Jun  1 07:17:24 2007

Tasks	Jobs/Min	JTI	Real	CPU	Jobs/sec/task
1	98.9		100	58.9	1.3	1.6482
101	5547.1		95	106.0	79.4	0.9154
201	6377.7		95	183.4	158.3	0.5288
301	6932.2		95	252.7	237.3	0.3838
401	7075.8		93	329.8	316.7	0.2941
501	7235.6		94	403.0	396.2	0.2407
600	7387.5		94	472.7	475.0	0.2052

Benchmark	Version	Machine	Run Date
AIM Multiuser Benchmark - Suite VII	"1.1"	vmemmap	Jun  1 09:59:04 2007

Tasks	Jobs/Min	JTI	Real	CPU	Jobs/sec/task
1	99.1		100	58.8	1.2	1.6509
101	5480.9		95	107.2	79.2	0.9044
201	6490.3		95	180.2	157.8	0.5382
301	6886.6		94	254.4	236.8	0.3813
401	7078.2		94	329.7	316.0	0.2942
501	7250.3		95	402.2	395.4	0.2412
600	7399.1		94	471.9	473.9	0.2055

open power 710 2 cpu, 4 Gb, SCSI and configured physically

Benchmark	Version	Machine	Run Date
AIM Multiuser Benchmark - Suite VII	"1.1"	extreme	May 29 15:42:53 2007

Tasks	Jobs/Min	JTI	Real	CPU	Jobs/sec/task
1	25.7		100	226.3	4.3	0.4286
101	1096.0		97	536.4	199.8	0.1809
201	1236.4		96	946.1	389.1	0.1025
301	1280.5		96	1368.0	582.3	0.0709
401	1270.2		95	1837.4	771.0	0.0528
501	1251.4		96	2330.1	955.9	0.0416
601	1252.6		96	2792.4	1139.2	0.0347
701	1245.2		96	3276.5	1334.6	0.0296
918	1229.5		96	4345.4	1728.7	0.0223

Benchmark	Version	Machine	Run Date
AIM Multiuser Benchmark - Suite VII	"1.1"	vmemmap	May 30 07:28:26 2007

Tasks	Jobs/Min	JTI	Real	CPU	Jobs/sec/task
1	25.6		100	226.9	4.3	0.4275
101	1049.3		97	560.2	198.1	0.1731
201	1199.1		97	975.6	390.7	0.0994
301	1261.7		96	1388.5	591.5	0.0699
401	1256.1		96	1858.1	771.9	0.0522
501	1220.1		96	2389.7	955.3	0.0406
601	1224.6		96	2856.3	1133.4	0.0340
701	1252.0		96	3258.7	1314.1	0.0298
915	1232.8		96	4319.7	1704.0	0.0225

amd64 2 2-core, 4Gb and SATA

Benchmark	Version	Machine	Run Date
AIM Multiuser Benchmark - Suite VII	"1.1"	extreme	Jun  2 03:59:48 2007

Tasks	Jobs/Min	JTI	Real	CPU	Jobs/sec/task
1	13.0		100	446.4	2.1	0.2173
101	533.4		97	1102.0	110.2	0.0880
201	578.3		97	2022.8	220.8	0.0480
301	583.8		97	3000.6	332.3	0.0323
401	580.5		97	4020.1	442.2	0.0241
501	574.8		98	5072.8	558.8	0.0191
600	566.5		98	6163.8	671.0	0.0157

Benchmark	Version	Machine	Run Date
AIM Multiuser Benchmark - Suite VII	"1.1"	vmemmap	Jun  3 04:19:31 2007

Tasks	Jobs/Min	JTI	Real	CPU	Jobs/sec/task
1	13.0		100	447.8	2.0	0.2166
101	536.5		97	1095.6	109.7	0.0885
201	567.7		97	2060.5	219.3	0.0471
301	582.1		96	3009.4	330.2	0.0322
401	578.2		96	4036.4	442.4	0.0240
501	585.1		98	4983.2	555.1	0.0195
600	565.5		98	6175.2	660.6	0.0157

This patch:

Fix some spelling errors.
Signed-off-by: NChristoph Lameter <clameter@sgi.com>
Signed-off-by: NAndy Whitcroft <apw@shadowen.org>
Acked-by: NMel Gorman <mel@csn.ul.ie>
Cc: "Luck, Tony" <tony.luck@intel.com>
Cc: Andi Kleen <ak@suse.de>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

As bi_end_io is only called once when the reqeust is complete,
the 'size' argument is now redundant.  Remove it.

Now there is no need for bio_endio to subtract the size completed
from bi_size.  So don't do that either.

While we are at it, change bi_end_io to return void.
Signed-off-by: NNeil Brown <neilb@suse.de>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

Hide everything in blkdev.h with CONFIG_BLOCK isn't set, and fixup
the (few) files that fail to build because they were relying on blkdev.h
pulling in extra includes for them.
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

find_lock_page increases page's usage count, we should decrease it
before return VM_FAULT_SIGBUS

Signed-off-by: Yan Zheng<yanzheng@21cn.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The test for VM_CAN_NONLINEAR always fails

Signed-off-by: Yan Zheng<yanzheng@21cn.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

All the current page_mkwrite() implementations also set the page dirty. Which
results in the set_page_dirty_balance() call to _not_ call balance, because the
page is already found dirty.

This allows us to dirty a _lot_ of pages without ever hitting
balance_dirty_pages().  Not good (tm).

Force a balance call if ->page_mkwrite() was successful.
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

When pinning and unpinning pagetables, we must protect them against
being used by other CPUs, lest they see the pagetable in an
intermediate read-only-but-not-pinned state.

When using split pte locks, doing this properly would require taking
all the pte locks for the pagetable while pinning, but this may overflow
the PREEMPT_BITS part of the preempt counter if the process has mapped
more than about 512M of memory.

However, failing to take the pte locks causes write-protect faults when
the pageout code is trying to clear the Access bit on a pte which is part
of a freshy created and still being pinned process after fork.

This is a short-term fix until the problem is solved properly.
Signed-off-by: NJeremy Fitzhardinge <jeremy@xensource.com>
Acked-by: NRik van Riel <riel@redhat.com>
Acked-by: NHugh Dickins <hugh@veritas.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andi Kleen <ak@suse.de>
Cc: Keir Fraser <keir@xensource.com>
Cc: Jan Beulich <jbeulich@novell.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>