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[PATCH] Use min of two prio settings in calculating distress for reclaim

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If try_to_free_pages / balance_pgdat are called with a gfp_mask specifying
GFP_IO and/or GFP_FS, they will reclaim the requisite number of pages, and the
reset prev_priority to DEF_PRIORITY (or to some other high (ie: unurgent)
value).

However, another reclaimer without those gfp_mask flags set (say, GFP_NOIO)
may still be struggling to reclaim pages.  The concurrent overwrite of
zone->prev_priority will cause this GFP_NOIO thread to unexpectedly cease
deactivating mapped pages, thus causing reclaim difficulties.

Fix this is to key the distress calculation not off zone->prev_priority, but
also take into account the local caller's priority by using
min(zone->prev_priority, sc->priority)

Signed-off-by: Martin J. Bligh <mbligh@google.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Martin Bligh 2006-10-28 10:38:25 -07:00 committed by Linus Torvalds
parent 3bb1a852ab
commit bbdb396a60
1 changed files with 4 additions and 4 deletions
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8
mm/vmscan.c
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@ -760,7 +760,7 @@ static inline int zone_is_near_oom(struct zone *zone)
* But we had to alter page->flags anyway.
*/
static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
struct scan_control *sc)
struct scan_control *sc, int priority)
{
unsigned long pgmoved;
int pgdeactivate = 0;
@ -784,7 +784,7 @@ static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
* `distress' is a measure of how much trouble we're having
* reclaiming pages. 0 -> no problems. 100 -> great trouble.
*/
distress = 100 >> zone->prev_priority;
distress = 100 >> min(zone->prev_priority, priority);
/*
* The point of this algorithm is to decide when to start
@ -936,7 +936,7 @@ static unsigned long shrink_zone(int priority, struct zone *zone,
nr_to_scan = min(nr_active,
(unsigned long)sc->swap_cluster_max);
nr_active -= nr_to_scan;
shrink_active_list(nr_to_scan, zone, sc);
shrink_active_list(nr_to_scan, zone, sc, priority);
}
if (nr_inactive) {
@ -1384,7 +1384,7 @@ static unsigned long shrink_all_zones(unsigned long nr_pages, int pass,
if (zone->nr_scan_active >= nr_pages || pass > 3) {
zone->nr_scan_active = 0;
nr_to_scan = min(nr_pages, zone->nr_active);
shrink_active_list(nr_to_scan, zone, sc);
shrink_active_list(nr_to_scan, zone, sc, prio);
}
}