linux/mm
Andy Whitcroft d41dee369b [PATCH] sparsemem memory model
Sparsemem abstracts the use of discontiguous mem_maps[].  This kind of
mem_map[] is needed by discontiguous memory machines (like in the old
CONFIG_DISCONTIGMEM case) as well as memory hotplug systems.  Sparsemem
replaces DISCONTIGMEM when enabled, and it is hoped that it can eventually
become a complete replacement.

A significant advantage over DISCONTIGMEM is that it's completely separated
from CONFIG_NUMA.  When producing this patch, it became apparent in that NUMA
and DISCONTIG are often confused.

Another advantage is that sparse doesn't require each NUMA node's ranges to be
contiguous.  It can handle overlapping ranges between nodes with no problems,
where DISCONTIGMEM currently throws away that memory.

Sparsemem uses an array to provide different pfn_to_page() translations for
each SECTION_SIZE area of physical memory.  This is what allows the mem_map[]
to be chopped up.

In order to do quick pfn_to_page() operations, the section number of the page
is encoded in page->flags.  Part of the sparsemem infrastructure enables
sharing of these bits more dynamically (at compile-time) between the
page_zone() and sparsemem operations.  However, on 32-bit architectures, the
number of bits is quite limited, and may require growing the size of the
page->flags type in certain conditions.  Several things might force this to
occur: a decrease in the SECTION_SIZE (if you want to hotplug smaller areas of
memory), an increase in the physical address space, or an increase in the
number of used page->flags.

One thing to note is that, once sparsemem is present, the NUMA node
information no longer needs to be stored in the page->flags.  It might provide
speed increases on certain platforms and will be stored there if there is
room.  But, if out of room, an alternate (theoretically slower) mechanism is
used.

This patch introduces CONFIG_FLATMEM.  It is used in almost all cases where
there used to be an #ifndef DISCONTIG, because SPARSEMEM and DISCONTIGMEM
often have to compile out the same areas of code.

Signed-off-by: Andy Whitcroft <apw@shadowen.org>
Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
Signed-off-by: Martin Bligh <mbligh@aracnet.com>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Yasunori Goto <y-goto@jp.fujitsu.com>
Signed-off-by: Bob Picco <bob.picco@hp.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-06-23 09:45:04 -07:00
..
bootmem.c [PATCH] sparsemem memory model 2005-06-23 09:45:04 -07:00
fadvise.c Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
filemap.c [PATCH] broken fault_in_pages_readable call in generic_file_buffered_write() 2005-06-06 14:42:23 -07:00
fremap.c Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
highmem.c [PATCH] count bounce buffer pages in vmstat 2005-05-01 08:58:37 -07:00
hugetlb.c [PATCH] Hugepage consolidation 2005-06-21 18:46:15 -07:00
internal.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
Kconfig [PATCH] sparsemem memory model 2005-06-23 09:45:04 -07:00
madvise.c [PATCH] madvise: merge the maps 2005-06-21 18:46:13 -07:00
Makefile [PATCH] sparsemem memory model 2005-06-23 09:45:04 -07:00
memory.c [PATCH] sparsemem memory model 2005-06-23 09:45:04 -07:00
mempolicy.c [PATCH] mbind: check_range use standard ptwalk 2005-06-21 18:46:19 -07:00
mempool.c [PATCH] use smp_mb/wmb/rmb where possible 2005-05-01 08:58:47 -07:00
mincore.c [PATCH] freepgt: sys_mincore ignore FIRST_USER_PGD_NR 2005-04-19 13:29:20 -07:00
mlock.c Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
mmap.c [PATCH] mmap topdown fix for large stack limit, large allocation 2005-06-21 18:46:16 -07:00
mprotect.c Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
mremap.c [PATCH] mm acct accounting fix 2005-05-17 07:59:12 -07:00
msync.c [PATCH] msync: check pte dirty earlier 2005-06-21 18:46:21 -07:00
nommu.c [PATCH] Avoiding mmap fragmentation 2005-06-21 18:46:16 -07:00
oom_kill.c [PATCH] add OOM debug 2005-06-21 18:46:17 -07:00
page_alloc.c [PATCH] sparsemem memory model 2005-06-23 09:45:04 -07:00
page_io.c Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
page-writeback.c [PATCH] DocBook: fix some descriptions 2005-05-01 08:59:26 -07:00
pdflush.c Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
prio_tree.c Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
readahead.c Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
rmap.c [PATCH] can_share_swap_page: use page_mapcount 2005-06-21 18:46:21 -07:00
shmem.c [PATCH] shmem: restore superblock info 2005-06-21 18:46:18 -07:00
slab.c [PATCH] Periodically drain non local pagesets 2005-06-21 18:46:18 -07:00
sparse.c [PATCH] sparsemem memory model 2005-06-23 09:45:04 -07:00
swap_state.c [PATCH] mm: use __GFP_NOMEMALLOC 2005-05-01 08:58:37 -07:00
swap.c Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
swapfile.c [PATCH] can_share_swap_page: use page_mapcount 2005-06-21 18:46:21 -07:00
thrash.c Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
tiny-shmem.c Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
truncate.c [PATCH] DocBook: fix some descriptions 2005-05-01 08:59:26 -07:00
vmalloc.c [PATCH] x86_64: Fixed guard page handling again in iounmap 2005-05-20 15:48:20 -07:00
vmscan.c [PATCH] vm: try_to_free_pages unused argument 2005-06-21 18:46:17 -07:00