This patchset follows up on the earlier work in Andrew's tree to reduce the
number of zones.  The patches allow to go to a minimum of 2 zones.  This one
allows also to make ZONE_DMA optional and therefore the number of zones can be
reduced to one.

ZONE_DMA is usually used for ISA DMA devices.  There are a number of reasons
why we would not want to have ZONE_DMA

1. Some arches do not need ZONE_DMA at all.

2. With the advent of IOMMUs DMA zones are no longer needed.
   The necessity of DMA zones may drastically be reduced
   in the future. This patchset allows a compilation of
   a kernel without that overhead.

3. Devices that require ISA DMA get rare these days. All
   my systems do not have any need for ISA DMA.

4. The presence of an additional zone unecessarily complicates
   VM operations because it must be scanned and balancing
   logic must operate on its.

5. With only ZONE_NORMAL one can reach the situation where
   we have only one zone. This will allow the unrolling of many
   loops in the VM and allows the optimization of varous
   code paths in the VM.

6. Having only a single zone in a NUMA system results in a
   1-1 correspondence between nodes and zones. Various additional
   optimizations to critical VM paths become possible.

Many systems today can operate just fine with a single zone.  If you look at
what is in ZONE_DMA then one usually sees that nothing uses it.  The DMA slabs
are empty (Some arches use ZONE_DMA instead of ZONE_NORMAL, then ZONE_NORMAL
will be empty instead).

On all of my systems (i386, x86_64, ia64) ZONE_DMA is completely empty.  Why
constantly look at an empty zone in /proc/zoneinfo and empty slab in
/proc/slabinfo?  Non i386 also frequently have no need for ZONE_DMA and zones
stay empty.

The patchset was tested on i386 (UP / SMP), x86_64 (UP, NUMA) and ia64 (NUMA).

The RFC posted earlier (see
http://marc.theaimsgroup.com/?l=linux-kernel&m=115231723513008&w=2) had lots
of #ifdefs in them.  An effort has been made to minize the number of #ifdefs
and make this as compact as possible.  The job was made much easier by the
ongoing efforts of others to extract common arch specific functionality.

I have been running this for awhile now on my desktop and finally Linux is
using all my available RAM instead of leaving the 16MB in ZONE_DMA untouched:

christoph@pentium940:~$ cat /proc/zoneinfo
Node 0, zone   Normal
  pages free     4435
        min      1448
        low      1810
        high     2172
        active   241786
        inactive 210170
        scanned  0 (a: 0 i: 0)
        spanned  524224
        present  524224
    nr_anon_pages 61680
    nr_mapped    14271
    nr_file_pages 390264
    nr_slab_reclaimable 27564
    nr_slab_unreclaimable 1793
    nr_page_table_pages 449
    nr_dirty     39
    nr_writeback 0
    nr_unstable  0
    nr_bounce    0
    cpu: 0 pcp: 0
              count: 156
              high:  186
              batch: 31
    cpu: 0 pcp: 1
              count: 9
              high:  62
              batch: 15
  vm stats threshold: 20
    cpu: 1 pcp: 0
              count: 177
              high:  186
              batch: 31
    cpu: 1 pcp: 1
              count: 12
              high:  62
              batch: 15
  vm stats threshold: 20
  all_unreclaimable: 0
  prev_priority:     12
  temp_priority:     12
  start_pfn:         0

This patch:

In two places in the VM we use ZONE_DMA to refer to the first zone.  If
ZONE_DMA is optional then other zones may be first.  So simply replace
ZONE_DMA with zone 0.

This also fixes ZONETABLE_PGSHIFT.  If we have only a single zone then
ZONES_PGSHIFT may become 0 because there is no need anymore to encode the zone
number related to a pgdat.  However, we still need a zonetable to index all
the zones for each node if this is a NUMA system.  Therefore define
ZONETABLE_SHIFT unconditionally as the offset of the ZONE field in page flags.

[apw@shadowen.org: fix mismerge]
Acked-by: NChristoph Hellwig <hch@infradead.org>
Signed-off-by: NChristoph Lameter <clameter@sgi.com>
Cc: Andi Kleen <ak@suse.de>
Cc: "Luck, Tony" <tony.luck@intel.com>
Cc: Kyle McMartin <kyle@mcmartin.ca>
Cc: Matthew Wilcox <willy@debian.org>
Cc: James Bottomley <James.Bottomley@steeleye.com>
Cc: Paul Mundt <lethal@linux-sh.org>
Signed-off-by: NAndy Whitcroft <apw@shadowen.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Values are available via ZVC sums.
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>

Function is unnecessary now.  We can use the summing features of the ZVCs to
get the values we need.
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>

nr_free_pages is now a simple access to a global variable.  Make it a macro
instead of a function.

The nr_free_pages now requires vmstat.h to be included.  There is one
occurrence in power management where we need to add the include.  Directly
refrer to global_page_state() there to clarify why the #include was added.

[akpm@osdl.org: arm build fix]
[akpm@osdl.org: sparc64 build fix]
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>

This is again simplifies some of the VM counter calculations through the use
of the ZVC consolidated counters.

[michal.k.k.piotrowski@gmail.com: build fix]
Signed-off-by: NChristoph Lameter <clameter@sgi.com>
Signed-off-by: NMichal Piotrowski <michal.k.k.piotrowski@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The determination of the dirty ratio to determine writeback behavior is
currently based on the number of total pages on the system.

However, not all pages in the system may be dirtied.  Thus the ratio is always
too low and can never reach 100%.  The ratio may be particularly skewed if
large hugepage allocations, slab allocations or device driver buffers make
large sections of memory not available anymore.  In that case we may get into
a situation in which f.e.  the background writeback ratio of 40% cannot be
reached anymore which leads to undesired writeback behavior.

This patchset fixes that issue by determining the ratio based on the actual
pages that may potentially be dirty.  These are the pages on the active and
the inactive list plus free pages.

The problem with those counts has so far been that it is expensive to
calculate these because counts from multiple nodes and multiple zones will
have to be summed up.  This patchset makes these counters ZVC counters.  This
means that a current sum per zone, per node and for the whole system is always
available via global variables and not expensive anymore to calculate.

The patchset results in some other good side effects:

- Removal of the various functions that sum up free, active and inactive
  page counts

- Cleanup of the functions that display information via the proc filesystem.

This patch:

The use of a ZVC for nr_inactive and nr_active allows a simplification of some
counter operations.  More ZVC functionality is used for sums etc in the
following patches.

[akpm@osdl.org: UP build fix]
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>

find_min_pfn_for_node() and find_min_pfn_with_active_regions() sort
early_node_map[] on every call.  This is an excessive amount of sorting and
that can be avoided.  This patch always searches the whole early_node_map[]
in find_min_pfn_for_node() instead of returning the first value found.  The
map is then only sorted once when required.  Successfully boot tested on a
number of machines.

[akpm@osdl.org: cleanup]
Signed-off-by: NMel Gorman <mel@csn.ul.ie>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Also split that long line up - people like to send us wordwrapped oom-kill
traces.

Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Christoph Lameter <clameter@engr.sgi.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This reverts commit e80ee884.

Pawel Sikora had a boot-time oops due to it - because the sign change
invalidates the following comparisons, since 'free_pages' can be
negative.

The micro-optimization just isn't worth it.
Bisected-by: NPawel Sikora <pluto@agmk.net>
Acked-by: NAndrew Morton <akpm@osdl.org>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Fix an oops experienced on the Cell architecture when init-time functions,
early_*(), are called at runtime.  It alters the call paths to make sure
that the callers explicitly say whether the call is being made on behalf of
a hotplug even, or happening at boot-time.

It has been compile tested on ppc64, ia64, s390, i386 and x86_64.
Acked-by: NArnd Bergmann <arndb@de.ibm.com>
Signed-off-by: NDave Hansen <haveblue@us.ibm.com>
Cc: Yasunori Goto <y-goto@jp.fujitsu.com>
Acked-by: NAndy Whitcroft <apw@shadowen.org>
Cc: Christoph Lameter <clameter@engr.sgi.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Acked-by: NHeiko Carstens <heiko.carstens@de.ibm.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Both process_zones() and drain_node_pages() check for populated zones
before touching pagesets.  However, __drain_pages does not do so,

This may result in a NULL pointer dereference for pagesets in unpopulated
zones if a NUMA setup is combined with cpu hotplug.

Initially the unpopulated zone has the pcp pointers pointing to the boot
pagesets.  Since the zone is not populated the boot pageset pointers will
not be changed during page allocator and slab bootstrap.

If a cpu is later brought down (first call to __drain_pages()) then the pcp
pointers for cpus in unpopulated zones are set to NULL since __drain_pages
does not first check for an unpopulated zone.

If the cpu is then brought up again then we call process_zones() which will
ignore the unpopulated zone.  So the pageset pointers will still be NULL.

If the cpu is then again brought down then __drain_pages will attempt to
drain pages by following the NULL pageset pointer for unpopulated zones.
Signed-off-by: NChristoph Lameter <clameter@sgi.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

At the moment the inode/dentry cache hash tables (common by way of
alloc_large_system_hash()) are incorrectly sized by their respective
detection logic when we attempt to use large base pages on systems with
little memory.

This results in odd behaviour when using a 64kB PAGE_SIZE, such as:

Dentry cache hash table entries: 8192 (order: -1, 32768 bytes)
Inode-cache hash table entries: 4096 (order: -2, 16384 bytes)

The mount cache hash table is seemingly the only one that gets this right
by directly taking PAGE_SIZE in to account.

The following patch attempts to catch the bogus values and round it up to
at least 0-order.
Signed-off-by: NPaul Mundt <lethal@linux-sh.org>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Elaborate the API for calling cpuset_zone_allowed(), so that users have to
explicitly choose between the two variants:

  cpuset_zone_allowed_hardwall()
  cpuset_zone_allowed_softwall()

Until now, whether or not you got the hardwall flavor depended solely on
whether or not you or'd in the __GFP_HARDWALL gfp flag to the gfp_mask
argument.

If you didn't specify __GFP_HARDWALL, you implicitly got the softwall
version.

Unfortunately, this meant that users would end up with the softwall version
without thinking about it.  Since only the softwall version might sleep,
this led to bugs with possible sleeping in interrupt context on more than
one occassion.

The hardwall version requires that the current tasks mems_allowed allows
the node of the specified zone (or that you're in interrupt or that
__GFP_THISNODE is set or that you're on a one cpuset system.)

The softwall version, depending on the gfp_mask, might allow a node if it
was allowed in the nearest enclusing cpuset marked mem_exclusive (which
requires taking the cpuset lock 'callback_mutex' to evaluate.)

This patch removes the cpuset_zone_allowed() call, and forces the caller to
explicitly choose between the hardwall and the softwall case.

If the caller wants the gfp_mask to determine this choice, they should (1)
be sure they can sleep or that __GFP_HARDWALL is set, and (2) invoke the
cpuset_zone_allowed_softwall() routine.

This adds another 100 or 200 bytes to the kernel text space, due to the few
lines of nearly duplicate code at the top of both cpuset_zone_allowed_*
routines.  It should save a few instructions executed for the calls that
turned into calls of cpuset_zone_allowed_hardwall, thanks to not having to
set (before the call) then check (within the call) the __GFP_HARDWALL flag.

For the most critical call, from get_page_from_freelist(), the same
instructions are executed as before -- the old cpuset_zone_allowed()
routine it used to call is the same code as the
cpuset_zone_allowed_softwall() routine that it calls now.

Not a perfect win, but seems worth it, to reduce this chance of hitting a
sleeping with irq off complaint again.
Signed-off-by: NPaul Jackson <pj@sgi.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Assign defaults most likely to please a new user:
 1) generate some logging output
    (verbose=2)
 2) avoid injecting failures likely to lock up UI
    (ignore_gfp_wait=1, ignore_gfp_highmem=1)
Signed-off-by: NDon Mullis <dwm@meer.net>
Cc: Akinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

This patch provides fault-injection capability for alloc_pages()

Boot option:

fail_page_alloc=<interval>,<probability>,<space>,<times>

	<interval> -- specifies the interval of failures.

	<probability> -- specifies how often it should fail in percent.

	<space> -- specifies the size of free space where memory can be
		   allocated safely in pages.

	<times> -- specifies how many times failures may happen at most.

Debugfs:

/debug/fail_page_alloc/interval
/debug/fail_page_alloc/probability
/debug/fail_page_alloc/specifies
/debug/fail_page_alloc/times
/debug/fail_page_alloc/ignore-gfp-highmem
/debug/fail_page_alloc/ignore-gfp-wait

Example:

	fail_page_alloc=10,100,0,-1

The page allocation (alloc_pages(), ...) fails once per 10 times.
Signed-off-by: NAkinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

This facility provides three entry points:

	ilog2()		Log base 2 of unsigned long
	ilog2_u32()	Log base 2 of u32
	ilog2_u64()	Log base 2 of u64

These facilities can either be used inside functions on dynamic data:

	int do_something(long q)
	{
		...;
		y = ilog2(x)
		...;
	}

Or can be used to statically initialise global variables with constant values:

	unsigned n = ilog2(27);

When performing static initialisation, the compiler will report "error:
initializer element is not constant" if asked to take a log of zero or of
something not reducible to a constant.  They treat negative numbers as
unsigned.

When not dealing with a constant, they fall back to using fls() which permits
them to use arch-specific log calculation instructions - such as BSR on
x86/x86_64 or SCAN on FRV - if available.

[akpm@osdl.org: MMC fix]
Signed-off-by: NDavid Howells <dhowells@redhat.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: David Howells <dhowells@redhat.com>
Cc: Wojtek Kaniewski <wojtekka@toxygen.net>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

 - move some file_operations structs into the .rodata section

 - move static strings from policy_types[] array into the .rodata section

 - fix generic seq_operations usages, so that those structs may be defined
   as "const" as well

[akpm@osdl.org: couple of fixes]
Signed-off-by: NHelge Deller <deller@gmx.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

There was lots of #ifdef noise in the kernel due to hotcpu_notifier(fn,
prio) not correctly marking 'fn' as used in the !HOTPLUG_CPU case, and thus
generating compiler warnings of unused symbols, hence forcing people to add
#ifdefs.

the compiler can skip truly unused functions just fine:

    text    data     bss     dec     hex filename
 1624412  728710 3674856 6027978  5bfaca vmlinux.before
 1624412  728710 3674856 6027978  5bfaca vmlinux.after

[akpm@osdl.org: topology.c fix]
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

It has no users and it's doubtful that we'll need it again.

Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Currently we we use the lru head link of the second page of a compound page
to hold its destructor.  This was ok when it was purely an internal
implmentation detail.  However, hugetlbfs overrides this destructor
violating the layering.  Abstract this out as explicit calls, also
introduce a type for the callback function allowing them to be type
checked.  For each callback we pre-declare the function, causing a type
error on definition rather than on use elsewhere.

[akpm@osdl.org: cleanups]
Signed-off-by: NAndy Whitcroft <apw@shadowen.org>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

The intent of GFP_THISNODE is to make sure that an allocation occurs on a
particular node.  If this is not possible then NULL needs to be returned so
that the caller can choose what to do next on its own (the slab allocator
depends on that).

However, GFP_THISNODE currently triggers reclaim before returning a failure
(GFP_THISNODE means GFP_NORETRY is set).  If we have over allocated a node
then we will currently do some reclaim before returning NULL.  The caller
may want memory from other nodes before reclaim should be triggered.  (If
the caller wants reclaim then he can directly use __GFP_THISNODE instead).

There is no flag to avoid reclaim in the page allocator and adding yet
another GFP_xx flag would be difficult given that we are out of available
flags.

So just compare and see if all bits for GFP_THISNODE (__GFP_THISNODE,
__GFP_NORETRY and __GFP_NOWARN) are set.  If so then we return NULL before
waking up kswapd.
Signed-off-by: NChristoph Lameter <clameter@sgi.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

These patches introduced new switch statements which are indented contrary
to the concensus in mm/*.c.  Fix them up to match that concensus.

    [PATCH] node local per-cpu-pages
    [PATCH] ZVC: Scale thresholds depending on the size of the system
    commit e7c8d5c9
    commit df9ecabaSigned-off-by: NAndy Whitcroft <apw@shadowen.org>
Cc: Christoph Lameter <clameter@engr.sgi.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

NUMA node ids are passed as either int or unsigned int almost exclusivly
page_to_nid and zone_to_nid both return unsigned long.  This is a throw
back to when page_to_nid was a #define and was thus exposing the real type
of the page flags field.

In addition to fixing up the definitions of page_to_nid and zone_to_nid I
audited the users of these functions identifying the following incorrect
uses:

1) mm/page_alloc.c show_node() -- printk dumping the node id,
2) include/asm-ia64/pgalloc.h pgtable_quicklist_free() -- comparison
   against numa_node_id() which returns an int from cpu_to_node(), and
3) mm/mpolicy.c check_pte_range -- used as an index in node_isset which
   uses bit_set which in generic code takes an int.
Signed-off-by: NAndy Whitcroft <apw@shadowen.org>
Cc: Christoph Lameter <clameter@engr.sgi.com>
Cc: "Luck, Tony" <tony.luck@intel.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

drain_node_pages() currently drains the complete pageset of all pages.  If
there are a large number of pages in the queues then we may hold off
interrupts for too long.

Duplicate the method used in free_hot_cold_page.  Only drain pcp->batch
pages at one time.
Signed-off-by: NChristoph Lameter <clameter@sgi.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

OOM can panic due to the processes stuck in __alloc_pages() doing infinite
rebalance loop while no memory can be reclaimed.  OOM killer tries to kill
some processes, but unfortunetaly, rebalance label was moved by someone
below the TIF_MEMDIE check, so buddy allocator doesn't see that process is
OOM-killed and it can simply fail the allocation :/

Observed in reality on RHEL4(2.6.9)+OpenVZ kernel when a user doing some
memory allocation tricks triggered OOM panic.
Signed-off-by: NDenis Lunev <den@sw.ru>
Signed-off-by: NKirill Korotaev <dev@openvz.org>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Add an arch_alloc_page to match arch_free_page.
Signed-off-by: NNick Piggin <npiggin@suse.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Optimize the critical zonelist scanning for free pages in the kernel memory
allocator by caching the zones that were found to be full recently, and
skipping them.

Remembers the zones in a zonelist that were short of free memory in the
last second.  And it stashes a zone-to-node table in the zonelist struct,
to optimize that conversion (minimize its cache footprint.)

Recent changes:

    This differs in a significant way from a similar patch that I
    posted a week ago.  Now, instead of having a nodemask_t of
    recently full nodes, I have a bitmask of recently full zones.
    This solves a problem that last weeks patch had, which on
    systems with multiple zones per node (such as DMA zone) would
    take seeing any of these zones full as meaning that all zones
    on that node were full.

    Also I changed names - from "zonelist faster" to "zonelist cache",
    as that seemed to better convey what we're doing here - caching
    some of the key zonelist state (for faster access.)

    See below for some performance benchmark results.  After all that
    discussion with David on why I didn't need them, I went and got
    some ;).  I wanted to verify that I had not hurt the normal case
    of memory allocation noticeably.  At least for my one little
    microbenchmark, I found (1) the normal case wasn't affected, and
    (2) workloads that forced scanning across multiple nodes for
    memory improved up to 10% fewer System CPU cycles and lower
    elapsed clock time ('sys' and 'real').  Good.  See details, below.

    I didn't have the logic in get_page_from_freelist() for various
    full nodes and zone reclaim failures correct.  That should be
    fixed up now - notice the new goto labels zonelist_scan,
    this_zone_full, and try_next_zone, in get_page_from_freelist().

There are two reasons I persued this alternative, over some earlier
proposals that would have focused on optimizing the fake numa
emulation case by caching the last useful zone:

 1) Contrary to what I said before, we (SGI, on large ia64 sn2 systems)
    have seen real customer loads where the cost to scan the zonelist
    was a problem, due to many nodes being full of memory before
    we got to a node we could use.  Or at least, I think we have.
    This was related to me by another engineer, based on experiences
    from some time past.  So this is not guaranteed.  Most likely, though.

    The following approach should help such real numa systems just as
    much as it helps fake numa systems, or any combination thereof.

 2) The effort to distinguish fake from real numa, using node_distance,
    so that we could cache a fake numa node and optimize choosing
    it over equivalent distance fake nodes, while continuing to
    properly scan all real nodes in distance order, was going to
    require a nasty blob of zonelist and node distance munging.

    The following approach has no new dependency on node distances or
    zone sorting.

See comment in the patch below for a description of what it actually does.

Technical details of note (or controversy):

 - See the use of "zlc_active" and "did_zlc_setup" below, to delay
   adding any work for this new mechanism until we've looked at the
   first zone in zonelist.  I figured the odds of the first zone
   having the memory we needed were high enough that we should just
   look there, first, then get fancy only if we need to keep looking.

 - Some odd hackery was needed to add items to struct zonelist, while
   not tripping up the custom zonelists built by the mm/mempolicy.c
   code for MPOL_BIND.  My usual wordy comments below explain this.
   Search for "MPOL_BIND".

 - Some per-node data in the struct zonelist is now modified frequently,
   with no locking.  Multiple CPU cores on a node could hit and mangle
   this data.  The theory is that this is just performance hint data,
   and the memory allocator will work just fine despite any such mangling.
   The fields at risk are the struct 'zonelist_cache' fields 'fullzones'
   (a bitmask) and 'last_full_zap' (unsigned long jiffies).  It should
   all be self correcting after at most a one second delay.

 - This still does a linear scan of the same lengths as before.  All
   I've optimized is making the scan faster, not algorithmically
   shorter.  It is now able to scan a compact array of 'unsigned
   short' in the case of many full nodes, so one cache line should
   cover quite a few nodes, rather than each node hitting another
   one or two new and distinct cache lines.

 - If both Andi and Nick don't find this too complicated, I will be
   (pleasantly) flabbergasted.

 - I removed the comment claiming we only use one cachline's worth of
   zonelist.  We seem, at least in the fake numa case, to have put the
   lie to that claim.

 - I pay no attention to the various watermarks and such in this performance
   hint.  A node could be marked full for one watermark, and then skipped
   over when searching for a page using a different watermark.  I think
   that's actually quite ok, as it will tend to slightly increase the
   spreading of memory over other nodes, away from a memory stressed node.

===============

Performance - some benchmark results and analysis:

This benchmark runs a memory hog program that uses multiple
threads to touch alot of memory as quickly as it can.

Multiple runs were made, touching 12, 38, 64 or 90 GBytes out of
the total 96 GBytes on the system, and using 1, 19, 37, or 55
threads (on a 56 CPU system.)  System, user and real (elapsed)
timings were recorded for each run, shown in units of seconds,
in the table below.

Two kernels were tested - 2.6.18-mm3 and the same kernel with
this zonelist caching patch added.  The table also shows the
percentage improvement the zonelist caching sys time is over
(lower than) the stock *-mm kernel.

      number     2.6.18-mm3	   zonelist-cache    delta (< 0 good)	percent
 GBs    N  	------------	   --------------    ----------------	systime
 mem threads   sys user  real	  sys  user  real     sys  user  real	 better
  12	 1     153   24   177	  151	 24   176      -2     0    -1	   1%
  12	19	99   22     8	   99	 22	8	0     0     0	   0%
  12	37     111   25     6	  112	 25	6	1     0     0	  -0%
  12	55     115   25     5	  110	 23	5      -5    -2     0	   4%
  38	 1     502   74   576	  497	 73   570      -5    -1    -6	   0%
  38	19     426   78    48	  373	 76    39     -53    -2    -9	  12%
  38	37     544   83    36	  547	 82    36	3    -1     0	  -0%
  38	55     501   77    23	  511	 80    24      10     3     1	  -1%
  64	 1     917  125  1042	  890	124  1014     -27    -1   -28	   2%
  64	19    1118  138   119	  965	141   103    -153     3   -16	  13%
  64	37    1202  151    94	 1136	150    81     -66    -1   -13	   5%
  64	55    1118  141    61	 1072	140    58     -46    -1    -3	   4%
  90	 1    1342  177  1519	 1275	174  1450     -67    -3   -69	   4%
  90	19    2392  199   192	 2116	189   176    -276   -10   -16	  11%
  90	37    3313  238   175	 2972	225   145    -341   -13   -30	  10%
  90	55    1948  210   104	 1843	213   100    -105     3    -4	   5%

Notes:
 1) This test ran a memory hog program that started a specified number N of
    threads, and had each thread allocate and touch 1/N'th of
    the total memory to be used in the test run in a single loop,
    writing a constant word to memory, one store every 4096 bytes.
    Watching this test during some earlier trial runs, I would see
    each of these threads sit down on one CPU and stay there, for
    the remainder of the pass, a different CPU for each thread.

 2) The 'real' column is not comparable to the 'sys' or 'user' columns.
    The 'real' column is seconds wall clock time elapsed, from beginning
    to end of that test pass.  The 'sys' and 'user' columns are total
    CPU seconds spent on that test pass.  For a 19 thread test run,
    for example, the sum of 'sys' and 'user' could be up to 19 times the
    number of 'real' elapsed wall clock seconds.

 3) Tests were run on a fresh, single-user boot, to minimize the amount
    of memory already in use at the start of the test, and to minimize
    the amount of background activity that might interfere.

 4) Tests were done on a 56 CPU, 28 Node system with 96 GBytes of RAM.

 5) Notice that the 'real' time gets large for the single thread runs, even
    though the measured 'sys' and 'user' times are modest.  I'm not sure what
    that means - probably something to do with it being slow for one thread to
    be accessing memory along ways away.  Perhaps the fake numa system, running
    ostensibly the same workload, would not show this substantial degradation
    of 'real' time for one thread on many nodes -- lets hope not.

 6) The high thread count passes (one thread per CPU - on 55 of 56 CPUs)
    ran quite efficiently, as one might expect.  Each pair of threads needed
    to allocate and touch the memory on the node the two threads shared, a
    pleasantly parallizable workload.

 7) The intermediate thread count passes, when asking for alot of memory forcing
    them to go to a few neighboring nodes, improved the most with this zonelist
    caching patch.

Conclusions:
 * This zonelist cache patch probably makes little difference one way or the
   other for most workloads on real numa hardware, if those workloads avoid
   heavy off node allocations.
 * For memory intensive workloads requiring substantial off-node allocations
   on real numa hardware, this patch improves both kernel and elapsed timings
   up to ten per-cent.
 * For fake numa systems, I'm optimistic, but will have to leave that up to
   Rohit Seth to actually test (once I get him a 2.6.18 backport.)
Signed-off-by: NPaul Jackson <pj@sgi.com>
Cc: Rohit Seth <rohitseth@google.com>
Cc: Christoph Lameter <clameter@engr.sgi.com>
Cc: David Rientjes <rientjes@cs.washington.edu>
Cc: Paul Menage <menage@google.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

The zone table is mostly not needed.  If we have a node in the page flags
then we can get to the zone via NODE_DATA() which is much more likely to be
already in the cpu cache.

In case of SMP and UP NODE_DATA() is a constant pointer which allows us to
access an exact replica of zonetable in the node_zones field.  In all of
the above cases there will be no need at all for the zone table.

The only remaining case is if in a NUMA system the node numbers do not fit
into the page flags.  In that case we make sparse generate a table that
maps sections to nodes and use that table to to figure out the node number.
 This table is sized to fit in a single cache line for the known 32 bit
NUMA platform which makes it very likely that the information can be
obtained without a cache miss.

For sparsemem the zone table seems to be have been fairly large based on
the maximum possible number of sections and the number of zones per node.
There is some memory saving by removing zone_table.  The main benefit is to
reduce the cache foootprint of the VM from the frequent lookups of zones.
Plus it simplifies the page allocator.

[akpm@osdl.org: build fix]
Signed-off-by: NChristoph Lameter <clameter@sgi.com>
Cc: Dave Hansen <haveblue@us.ibm.com>
Cc: Andy Whitcroft <apw@shadowen.org>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

- s/freeliest/freelist/ spelling fix

- Check for NULL *z zone seems useless - even if it could happen, so
  what?  Perhaps we should have a check later on if we are faced with an
  allocation request that is not allowed to fail - shouldn't that be a
  serious kernel error, passing an empty zonelist with a mandate to not
  fail?

- Initializing 'z' to zonelist->zones can wait until after the first
  get_page_from_freelist() fails; we only use 'z' in the wakeup_kswapd()
  loop, so let's initialize 'z' there, in a 'for' loop.  Seems clearer.

- Remove superfluous braces around a break

- Fix a couple errant spaces

- Adjust indentation on the cpuset_zone_allowed() check, to match the
  lines just before it -- seems easier to read in this case.

- Add another set of braces to the zone_watermark_ok logic

From: Paul Jackson <pj@sgi.com>

  Backout one item from a previous "memory page_alloc minor cleanups" patch.
   Until and unless we are certain that no one can ever pass an empty zonelist
  to __alloc_pages(), this check for an empty zonelist (or some BUG
  equivalent) is essential.  The code in get_page_from_freelist() blow ups if
  passed an empty zonelist.
Signed-off-by: NPaul Jackson <pj@sgi.com>
Acked-by: NChristoph Lameter <clameter@sgi.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: NPaul Jackson <pj@sgi.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

find_min_pfn_for_node() and find_min_pfn_with_active_regions() both
depend on a sorted early_node_map[].  However, sort_node_map() is being
called after fin_min_pfn_with_active_regions() in
free_area_init_nodes().

In most cases, this is ok, but on at least one x86_64, the SRAT table
caused the E820 ranges to be registered out of order.  This gave the
wrong values for the min PFN range resulting in some pages not being
initialised.

This patch sorts the early_node_map in find_min_pfn_for_node().  It has
been boot tested on x86, x86_64, ppc64 and ia64.
Signed-off-by: NMel Gorman <mel@csn.ul.ie>
Acked-by: NAndre Noll <maan@systemlinux.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Un-needed add-store operation wastes a few bytes.
8 bytes wasted with -O2, on a ppc.
Signed-off-by: Nnkalmala <nkalmala@gmail.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

absent_pages_in_range() made the assumption that users of the
arch-independent zone-sizing API would not care about holes beyound the end
of physical memory.  This was not the case and was "fixed" in a patch
called "Account for holes that are outside the range of physical memory".
However, when given a range that started before a hole in "real" memory and
ended beyond the end of memory, it would get the result wrong.  The bug is
in mainline but a patch is below.

It has been tested successfully on a number of machines and architectures.
Additional credit to Keith Mannthey for discovering the problem, helping
identify the correct fix and confirming it Worked For Him.
Signed-off-by: NMel Gorman <mel@csn.ul.ie>
Cc: keith mannthey <kmannth@us.ibm.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

The temp_priority field in zone is racy, as we can walk through a reclaim
path, and just before we copy it into prev_priority, it can be overwritten
(say with DEF_PRIORITY) by another reclaimer.

The same bug is contained in both try_to_free_pages and balance_pgdat, but
it is fixed slightly differently.  In balance_pgdat, we keep a separate
priority record per zone in a local array.  In try_to_free_pages there is
no need to do this, as the priority level is the same for all zones that we
reclaim from.

Impact of this bug is that temp_priority is copied into prev_priority, and
setting this artificially high causes reclaimers to set distress
artificially low.  They then fail to reclaim mapped pages, when they are,
in fact, under severe memory pressure (their priority may be as low as 0).
This causes the OOM killer to fire incorrectly.

From: Andrew Morton <akpm@osdl.org>

__zone_reclaim() isn't modifying zone->prev_priority.  But zone->prev_priority
is used in the decision whether or not to bring mapped pages onto the inactive
list.  Hence there's a risk here that __zone_reclaim() will fail because
zone->prev_priority ir large (ie: low urgency) and lots of mapped pages end up
stuck on the active list.

Fix that up by decreasing (ie making more urgent) zone->prev_priority as
__zone_reclaim() scans the zone's pages.

This bug perhaps explains why ZONE_RECLAIM_PRIORITY was created.  It should be
possible to remove that now, and to just start out at DEF_PRIORITY?

Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Christoph Lameter <clameter@engr.sgi.com>
Cc: <stable@kernel.org>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Reintroduce NODES_SPAN_OTHER_NODES for powerpc

Revert "[PATCH] Remove SPAN_OTHER_NODES config definition"
    This reverts commit f62859bb.
Revert "[PATCH] mm: remove arch independent NODES_SPAN_OTHER_NODES"
    This reverts commit a94b3ab7.

Also update the comments to indicate that this is still required
and where its used.
Signed-off-by: NAndy Whitcroft <apw@shadowen.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Mike Kravetz <kravetz@us.ibm.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Acked-by: NMel Gorman <mel@csn.ul.ie>
Acked-by: NWill Schmidt <will_schmidt@vnet.ibm.com>
Cc: Christoph Lameter <clameter@sgi.com>
Cc: <stable@kernel.org>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Qooting Adrian:

- net/sunrpc/svc.c uses highest_possible_node_id()

- include/linux/nodemask.h says highest_possible_node_id() is
  out-of-line #if MAX_NUMNODES > 1

- the out-of-line highest_possible_node_id() is in lib/cpumask.c

- lib/Makefile: lib-$(CONFIG_SMP) += cpumask.o
  CONFIG_ARCH_DISCONTIGMEM_ENABLE=y, CONFIG_SMP=n, CONFIG_SUNRPC=y

-> highest_possible_node_id() is used in net/sunrpc/svc.c
   CONFIG_NODES_SHIFT defined and > 0

-> include/linux/numa.h: MAX_NUMNODES > 1

-> compile error

The bug is not present on architectures where ARCH_DISCONTIGMEM_ENABLE
depends on NUMA (but m32r isn't the only affected architecture).

So move the function into page_alloc.c

Cc: Adrian Bunk <bunk@stusta.de>
Cc: Paul Jackson <pj@sgi.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Separate out the concept of "queue congestion" from "backing-dev congestion".
Congestion is a backing-dev concept, not a queue concept.

The blk_* congestion functions are retained, as wrappers around the core
backing-dev congestion functions.

This proper layering is needed so that NFS can cleanly use the congestion
functions, and so that CONFIG_BLOCK=n actually links.

Cc: "Thomas Maier" <balagi@justmail.de>
Cc: "Jens Axboe" <jens.axboe@oracle.com>
Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
Cc: David Howells <dhowells@redhat.com>
Cc: Peter Osterlund <petero2@telia.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Move the lock debug checks below the page reserved checks.  Also, having
debug_check_no_locks_freed in kernel_map_pages is wrong.
Signed-off-by: NNick Piggin <npiggin@suse.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

After the PG_reserved check was added, arch_free_page was being called in the
wrong place (it could be called for a page we don't actually want to free).
Fix that.
Signed-off-by: NNick Piggin <npiggin@suse.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

memmap_zone_idx() is not used anymore.  It was required by an earlier
version of
account-for-memmap-and-optionally-the-kernel-image-as-holes.patch but not
any more.
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Fix kernel-doc and function declaration (missing "void") in
mm/page_alloc.c.

Add mm/page_alloc.c to kernel-api.tmpl in DocBook.

mm/page_alloc.c:2589:38: warning: non-ANSI function declaration of function 'remove_all_active_ranges'
Signed-off-by: NRandy Dunlap <rdunlap@xenotime.net>
Acked-by: NChristoph Lameter <clameter@sgi.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>