linux.git/mm/page_alloc.c, branch v2.6.21.7

[PATCH] Rename PG_checked to PG_owner_priv_1

2007-03-01T22:53:37+00:00

Rename PG_checked to PG_owner_priv_1 to reflect its availablilty as a
private flag for use by the owner/allocator of the page.  In the case of
pagecache pages (which might be considered to be owned by the mm),
filesystems may use the flag.

Signed-off-by: Jeremy Fitzhardinge 
Signed-off-by: Nick Piggin 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] slab: reduce size of alien cache to cover only possible nodes

2007-02-21T01:10:13+00:00

The alien cache is a per cpu per node array allocated for every slab on the
system.  Currently we size this array for all nodes that the kernel does
support.  For IA64 this is 1024 nodes.  So we allocate an array with 1024
objects even if we only boot a system with 4 nodes.

This patch uses "nr_node_ids" to determine the number of possible nodes
supported by a hardware configuration and only allocates an alien cache
sized for possible nodes.

The initialization of nr_node_ids occurred too late relative to the bootstrap
of the slab allocator and so I moved the setup_nr_node_ids() into
free_area_init_nodes().

Signed-off-by: Christoph Lameter 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] Replace highest_possible_node_id() with nr_node_ids

2007-02-21T01:10:13+00:00

highest_possible_node_id() is currently used to calculate the last possible
node idso that the network subsystem can figure out how to size per node
arrays.

I think having the ability to determine the maximum amount of nodes in a
system at runtime is useful but then we should name this entry
correspondingly, it should return the number of node_ids, and the the value
needs to be setup only once on bootup.  The node_possible_map does not
change after bootup.

This patch introduces nr_node_ids and replaces the use of
highest_possible_node_id().  nr_node_ids is calculated on bootup when the
page allocators pagesets are initialized.

[deweerdt@free.fr: fix oops]
Signed-off-by: Christoph Lameter 
Cc: Neil Brown 
Cc: Trond Myklebust 
Signed-off-by: Frederik Deweerdt 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] optional ZONE_DMA: optional ZONE_DMA in the VM

2007-02-11T18:51:18+00:00

Make ZONE_DMA optional in core code.

- ifdef all code for ZONE_DMA and related definitions following the example
  for ZONE_DMA32 and ZONE_HIGHMEM.

- Without ZONE_DMA, ZONE_HIGHMEM and ZONE_DMA32 we get to a ZONES_SHIFT of
  0.

- Modify the VM statistics to work correctly without a DMA zone.

- Modify slab to not create DMA slabs if there is no ZONE_DMA.

[akpm@osdl.org: cleanup]
[jdike@addtoit.com: build fix]
[apw@shadowen.org: Simplify calculation of the number of bits we need for ZONES_SHIFT]
Signed-off-by: Christoph Lameter 
Cc: Andi Kleen 
Cc: "Luck, Tony" 
Cc: Kyle McMartin 
Cc: Matthew Wilcox 
Cc: James Bottomley 
Cc: Paul Mundt 
Signed-off-by: Andy Whitcroft 
Signed-off-by: Jeff Dike 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] optional ZONE_DMA: deal with cases of ZONE_DMA meaning the first zone

2007-02-11T18:51:18+00:00

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: Christoph Hellwig 
Signed-off-by: Christoph Lameter 
Cc: Andi Kleen 
Cc: "Luck, Tony" 
Cc: Kyle McMartin 
Cc: Matthew Wilcox 
Cc: James Bottomley 
Cc: Paul Mundt 
Signed-off-by: Andy Whitcroft 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] Drop get_zone_counts()

2007-02-11T18:51:18+00:00

Values are available via ZVC sums.

Signed-off-by: Christoph Lameter 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] Drop nr_free_pages_pgdat()

2007-02-11T18:51:18+00:00

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

Signed-off-by: Christoph Lameter 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] Drop free_pages()

2007-02-11T18:51:18+00:00

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: Christoph Lameter 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] Use ZVC for free_pages

2007-02-11T18:51:17+00:00

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: Christoph Lameter 
Signed-off-by: Michal Piotrowski 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] Use ZVC for inactive and active counts

2007-02-11T18:51:17+00:00

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: Christoph Lameter 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds