V1 -> V3:
+ rebase to 23-mm1 atop RvR's split LRU series
+ define NR_NORECLAIM and LRU_NORECLAIM to avoid errors when not
configured.
V1 -> V2:
+ handle review comments -- various typos and errors.
+ extract "putback_all_noreclaim_pages()" into a separate patch
and rework as "scan_all_zones_noreclaim_pages().
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 "nonreclaimable" pages on a separate per-zone LRU list,
to "hide" them from vmscan. A separate noreclaim pagevec is provided
for shrink_active_list() to move nonreclaimable pages to the noreclaim
list without over burdening the zone lru_lock.
Pages on the noreclaim list have both PG_noreclaim and PG_lru set.
Thus, PG_noreclaim is analogous to and mutually exclusive with
PG_active--it specifies which LRU list the page is on.
The noreclaim infrastructure is enabled by a new mm Kconfig option
[CONFIG_]NORECLAIM.
A new function 'page_reclaimable(page, vma)' in vmscan.c tests whether
or not a page is reclaimable. Subsequent patches will add the various
!reclaimable tests. We'll want to keep these tests light-weight for
use in shrink_active_list() and, possibly, the fault path.
Notes:
1. for now, use bit 30 in page flags. This restricts the no reclaim
infrastructure to 64-bit systems. [The mlock patch, later in this
series, uses another of these 64-bit-system-only flags.]
Rationale: 32-bit systems have no free page flags and are less
likely to have the large amounts of memory that exhibit the problems
this series attempts to solve. [I'm sure someone will disabuse me
of this notion.]
Thus, NORECLAIM currently depends on [CONFIG_]64BIT.
2. The pagevec to move pages to the noreclaim list results in another
loop at the end of shrink_active_list(). If we ultimately adopt Rik
van Riel's split lru approach, I think we'll need to find a way to
factor all of t...
