• Lee Schermerhorn's avatar
    Unevictable LRU Infrastructure · 894bc310
    Lee Schermerhorn authored
    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: default avatarLee Schermerhorn <lee.schermerhorn@hp.com>
    Signed-off-by: default avatarRik van Riel <riel@redhat.com>
    Signed-off-by: default avatarKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
    Debugged-by: default avatarBenjamin Kidwell <benjkidwell@yahoo.com>
    Signed-off-by: default avatarDaisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
    Signed-off-by: default avatarKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    894bc310
pagevec.h 2.64 KB