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authorLee Schermerhorn <Lee.Schermerhorn@hp.com>2008-10-18 20:26:39 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2008-10-20 08:50:26 -0700
commit894bc310419ac95f4fa4142dc364401a7e607f65 (patch)
tree15d56a7333b41620016b845d2323dd06e822b621 /mm/Kconfig
parent8a7a8544a4f6554ec2d8048ac9f9672f442db5a2 (diff)
downloadconfigs-894bc310419ac95f4fa4142dc364401a7e607f65.tar.gz
Unevictable LRU Infrastructure
When the system contains lots of mlocked or otherwise unevictable pages, the pageout code (kswapd) can spend lots of time scanning over these pages. Worse still, the presence of lots of unevictable pages can confuse kswapd into thinking that more aggressive pageout modes are required, resulting in all kinds of bad behaviour. Infrastructure to manage pages excluded from reclaim--i.e., hidden from vmscan. Based on a patch by Larry Woodman of Red Hat. Reworked to maintain "unevictable" pages on a separate per-zone LRU list, to "hide" them from vmscan. Kosaki Motohiro added the support for the memory controller unevictable lru list. Pages on the unevictable list have both PG_unevictable and PG_lru set. Thus, PG_unevictable is analogous to and mutually exclusive with PG_active--it specifies which LRU list the page is on. The unevictable infrastructure is enabled by a new mm Kconfig option [CONFIG_]UNEVICTABLE_LRU. A new function 'page_evictable(page, vma)' in vmscan.c tests whether or not a page may be evictable. Subsequent patches will add the various !evictable tests. We'll want to keep these tests light-weight for use in shrink_active_list() and, possibly, the fault path. To avoid races between tasks putting pages [back] onto an LRU list and tasks that might be moving the page from non-evictable to evictable state, the new function 'putback_lru_page()' -- inverse to 'isolate_lru_page()' -- tests the "evictability" of a page after placing it on the LRU, before dropping the reference. If the page has become unevictable, putback_lru_page() will redo the 'putback', thus moving the page to the unevictable list. This way, we avoid "stranding" evictable pages on the unevictable list. [akpm@linux-foundation.org: fix fallout from out-of-order merge] [riel@redhat.com: fix UNEVICTABLE_LRU and !PROC_PAGE_MONITOR build] [nishimura@mxp.nes.nec.co.jp: remove redundant mapping check] [kosaki.motohiro@jp.fujitsu.com: unevictable-lru-infrastructure: putback_lru_page()/unevictable page handling rework] [kosaki.motohiro@jp.fujitsu.com: kill unnecessary lock_page() in vmscan.c] [kosaki.motohiro@jp.fujitsu.com: revert migration change of unevictable lru infrastructure] [kosaki.motohiro@jp.fujitsu.com: revert to unevictable-lru-infrastructure-kconfig-fix.patch] [kosaki.motohiro@jp.fujitsu.com: restore patch failure of vmstat-unevictable-and-mlocked-pages-vm-events.patch] 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> Debugged-by: Benjamin Kidwell <benjkidwell@yahoo.com> Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/Kconfig')
-rw-r--r--mm/Kconfig11
1 files changed, 11 insertions, 0 deletions
diff --git a/mm/Kconfig b/mm/Kconfig
index 1a501a4de95..5b5790f8a81 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -209,5 +209,16 @@ config VIRT_TO_BUS
def_bool y
depends on !ARCH_NO_VIRT_TO_BUS
+config UNEVICTABLE_LRU
+ bool "Add LRU list to track non-evictable pages"
+ default y
+ depends on MMU
+ help
+ Keeps unevictable pages off of the active and inactive pageout
+ lists, so kswapd will not waste CPU time or have its balancing
+ algorithms thrown off by scanning these pages. Selecting this
+ will use one page flag and increase the code size a little,
+ say Y unless you know what you are doing.
+
config MMU_NOTIFIER
bool