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SHM_LOCKED pages are unevictable

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Shmem segments locked into memory via shmctl(SHM_LOCKED) should not be
kept on the normal LRU, since scanning them is a waste of time and might
throw off kswapd's balancing algorithms.  Place them on the unevictable
LRU list instead.

Use the AS_UNEVICTABLE flag to mark address_space of SHM_LOCKed shared
memory regions as unevictable.  Then these pages will be culled off the
normal LRU lists during vmscan.

Add new wrapper function to clear the mapping's unevictable state when/if
shared memory segment is munlocked.

Add 'scan_mapping_unevictable_page()' to mm/vmscan.c to scan all pages in
the shmem segment's mapping [struct address_space] for evictability now
that they're no longer locked.  If so, move them to the appropriate zone
lru list.

Changes depend on [CONFIG_]UNEVICTABLE_LRU.

[kosaki.motohiro@jp.fujitsu.com: revert shm change]
Signed-off-by: Lee Schermerhorn <lee.schermerhorn@hp.com>
Signed-off-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Kosaki Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Lee Schermerhorn
2008-10-18 20:26:43 -07:00
committed by Linus Torvalds
parent ba9ddf4939
commit 89e004ea55
6 changed files with 112 additions and 5 deletions
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12
include/linux/pagemap.h
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@@ -40,14 +40,20 @@ static inline void mapping_set_unevictable(struct address_space *mapping)
set_bit(AS_UNEVICTABLE, &mapping->flags);
}
static inline void mapping_clear_unevictable(struct address_space *mapping)
{
clear_bit(AS_UNEVICTABLE, &mapping->flags);
}
static inline int mapping_unevictable(struct address_space *mapping)
{
if (mapping && (mapping->flags & AS_UNEVICTABLE))
return 1;
return 0;
if (likely(mapping))
return test_bit(AS_UNEVICTABLE, &mapping->flags);
return !!mapping;
}
#else
static inline void mapping_set_unevictable(struct address_space *mapping) { }
static inline void mapping_clear_unevictable(struct address_space *mapping) { }
static inline int mapping_unevictable(struct address_space *mapping)
{
return 0;