linux-toradex.git/include/linux/page-flags.h, branch v2.6.20.21

VM: Remove "clear_page_dirty()" and "test_clear_page_dirty()" functions

2006-12-21T17:19:57+00:00

They were horribly easy to mis-use because of their tempting naming, and
they also did way more than any users of them generally wanted them to
do.

A dirty page can become clean under two circumstances:

 (a) when we write it out.  We have "clear_page_dirty_for_io()" for
     this, and that function remains unchanged.

     In the "for IO" case it is not sufficient to just clear the dirty
     bit, you also have to mark the page as being under writeback etc.

 (b) when we actually remove a page due to it becoming inaccessible to
     users, notably because it was truncate()'d away or the file (or
     metadata) no longer exists, and we thus want to cancel any
     outstanding dirty state.

For the (b) case, we now introduce "cancel_dirty_page()", which only
touches the page state itself, and verifies that the page is not mapped
(since cancelling writes on a mapped page would be actively wrong as it
is still accessible to users).

Some filesystems need to be fixed up for this: CIFS, FUSE, JFS,
ReiserFS, XFS all use the old confusing functions, and will be fixed
separately in subsequent commits (with some of them just removing the
offending logic, and others using clear_page_dirty_for_io()).

This was confirmed by Martin Michlmayr to fix the apt database
corruption on ARM.

Cc: Martin Michlmayr 
Cc: Peter Zijlstra 
Cc: Hugh Dickins 
Cc: Nick Piggin 
Cc: Arjan van de Ven 
Cc: Andrei Popa 
Cc: Andrew Morton 
Cc: Dave Kleikamp 
Cc: Gordon Farquharson 
Cc: Martin Schwidefsky 
Cc: Trond Myklebust 
Signed-off-by: Linus Torvalds

[PATCH] convert s390 page handling macros to functions

2006-09-29T16:18:03+00:00

Convert s390 page handling macros to functions.  In particular this fixes a
problem with s390's SetPageUptodate macro which uses its input parameter
twice which again can cause subtle bugs.

[akpm@osdl.org: build fix]
Cc: Martin Schwidefsky 
Signed-off-by: Heiko Carstens 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] update some mm/ comments

2006-09-26T15:48:49+00:00

Let's try to keep mm/ comments more useful and up to date. This is a start.

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

[PATCH] zoned vm counters: conversion of nr_writeback to per zone counter

2006-06-30T18:25:35+00:00

Conversion of nr_writeback to per zone counter.

This removes the last page_state counter from arch/i386/mm/pgtable.c so we
drop the page_state from there.

[akpm@osdl.org: bugfix]
Signed-off-by: Christoph Lameter 
Cc: Trond Myklebust 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] zoned vm counters: create vmstat.c/.h from page_alloc.c/.h

2006-06-30T18:25:34+00:00

NOTE: ZVC are *not* the lightweight event counters.  ZVCs are reliable whereas
event counters do not need to be.

Zone based VM statistics are necessary to be able to determine what the state
of memory in one zone is.  In a NUMA system this can be helpful for local
reclaim and other memory optimizations that may be able to shift VM load in
order to get more balanced memory use.

It is also useful to know how the computing load affects the memory
allocations on various zones.  This patchset allows the retrieval of that data
from userspace.

The patchset introduces a framework for counters that is a cross between the
existing page_stats --which are simply global counters split per cpu-- and the
approach of deferred incremental updates implemented for nr_pagecache.

Small per cpu 8 bit counters are added to struct zone.  If the counter exceeds
certain thresholds then the counters are accumulated in an array of
atomic_long in the zone and in a global array that sums up all zone values.
The small 8 bit counters are next to the per cpu page pointers and so they
will be in high in the cpu cache when pages are allocated and freed.

Access to VM counter information for a zone and for the whole machine is then
possible by simply indexing an array (Thanks to Nick Piggin for pointing out
that approach).  The access to the total number of pages of various types does
no longer require the summing up of all per cpu counters.

Benefits of this patchset right now:

- Ability for UP and SMP configuration to determine how memory
  is balanced between the DMA, NORMAL and HIGHMEM zones.

- loops over all processors are avoided in writeback and
  reclaim paths. We can avoid caching the writeback information
  because the needed information is directly accessible.

- Special handling for nr_pagecache removed.

- zone_reclaim_interval vanishes since VM stats can now determine
  when it is worth to do local reclaim.

- Fast inline per node page state determination.

- Accurate counters in /sys/devices/system/node/node*/meminfo. Current
  counters are counting simply which processor allocated a page somewhere
  and guestimate based on that. So the counters were not useful to show
  the actual distribution of page use on a specific zone.

- The swap_prefetch patch requires per node statistics in order to
  figure out when processors of a node can prefetch. This patch provides
  some of the needed numbers.

- Detailed VM counters available in more /proc and /sys status files.

References to earlier discussions:
V1 http://marc.theaimsgroup.com/?l=linux-kernel&m=113511649910826&w=2
V2 http://marc.theaimsgroup.com/?l=linux-kernel&m=114980851924230&w=2
V3 http://marc.theaimsgroup.com/?l=linux-kernel&m=115014697910351&w=2
V4 http://marc.theaimsgroup.com/?l=linux-kernel&m=115024767318740&w=2

Performance tests with AIM7 did not show any regressions.  Seems to be a tad
faster even.  Tested on ia64/NUMA.  Builds fine on i386, SMP / UP.  Includes
fixes for s390/arm/uml arch code.

This patch:

Move counter code from page_alloc.c/page-flags.h to vmstat.c/h.

Create vmstat.c/vmstat.h by separating the counter code and the proc
functions.

Move the vm_stat_text array before zoneinfo_show.

[akpm@osdl.org: s390 build fix]
[akpm@osdl.org: HOTPLUG_CPU build fix]
Signed-off-by: Christoph Lameter 
Cc: Heiko Carstens 
Cc: Martin Schwidefsky 
Cc: Trond Myklebust 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] PG_uncached is ia64 only

2006-06-23T14:42:46+00:00

As Nick points out, only ia64 uses PG_uncached.  So we can push it up into the
higher bits of the lower half of page->flags and make room for another flag on
32-bit machines.

Cc: "Luck, Tony" 
Cc: Jesse Barnes 
Cc: Jes Sorensen 
Cc: Nick Piggin 
Cc: Andy Whitcroft 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] page flags: add commentry regarding field reservation

2006-04-11T13:18:32+00:00

Add some documentation regarding the utilisation of the flags field in
struct page.  This field is overloaded for per page bits and to hold node,
zone and SPARSEMEM information.  Make it clear which areas are used for
what and how many bits are in each area.

Signed-off-by: Andy Whitcroft 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] Fix buddy list race that could lead to page lru list corruptions

2006-04-10T17:16:37+00:00

Rohit found an obscure bug causing buddy list corruption.

page_is_buddy is using a non-atomic test (PagePrivate && page_count == 0)
to determine whether or not a free page's buddy is itself free and in the
buddy lists.

Each of the conjuncts may be true at different times due to unrelated
conditions, so the non-atomic page_is_buddy test may find each conjunct to
be true even if they were not both true at the same time (ie. the page was
not on the buddy lists).

Signed-off-by: Martin Bligh 
Signed-off-by: Rohit Seth 
Signed-off-by: Nick Piggin 
Signed-off-by: KAMEZAWA Hiroyuki 
Signed-off-by: Linus Torvalds

[PATCH] mm: page_state comment more

2006-03-22T15:53:58+00:00

Clarify that preemption needs to be guarded against with the
__xxx_page_state functions.

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

[PATCH] mm: slab less atomics

2006-03-22T15:53:57+00:00

Atomic operation removal from slab

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