OpenE2K
/
linux
6
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

mm: vmscan: save work scanning (almost) empty LRU lists 

In certain cases (kswapd reclaim, memcg target reclaim), a fixed minimum
amount of pages is scanned from the LRU lists on each iteration, to make
progress.

Do not make this minimum bigger than the respective LRU list size,
however, and save some busy work trying to isolate and reclaim pages
that are not there.

Empty LRU lists are quite common with memory cgroups in NUMA
environments because there exists a set of LRU lists for each zone for
each memory cgroup, while the memory of a single cgroup is expected to
stay on just one node.  The number of expected empty LRU lists is thus

  memcgs * (nodes - 1) * lru types

Each attempt to reclaim from an empty LRU list does expensive size
comparisons between lists, acquires the zone's lru lock etc.  Avoid
that.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Rik van Riel <riel@redhat.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Cc: Hugh Dickins <hughd@google.com>
Cc: Satoru Moriya <satoru.moriya@hds.com>
Cc: Simon Jeons <simon.jeons@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Johannes Weiner 2013-02-22 16:32:12 -08:00 committed by Linus Torvalds
parent 7c5bd705d8
commit d778df51c0
2 changed files with 7 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
include/linux/swap.h
View File

@ -156,7 +156,7 @@ enum {
SWP_SCANNING = (1 << 8), /* refcount in scan_swap_map */
};
#define SWAP_CLUSTER_MAX 32
#define SWAP_CLUSTER_MAX 32UL
#define COMPACT_CLUSTER_MAX SWAP_CLUSTER_MAX
/*

10
mm/vmscan.c
View File

@ -1761,15 +1761,17 @@ static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc,
out:
for_each_evictable_lru(lru) {
int file = is_file_lru(lru);
unsigned long size;
unsigned long scan;
scan = get_lru_size(lruvec, lru);
size = get_lru_size(lruvec, lru);
if (sc->priority || noswap || !vmscan_swappiness(sc)) {
scan >>= sc->priority;
scan = size >> sc->priority;
if (!scan && force_scan)
scan = SWAP_CLUSTER_MAX;
scan = min(size, SWAP_CLUSTER_MAX);
scan = div64_u64(scan * fraction[file], denominator);
}
} else
scan = size;
nr[lru] = scan;
}
}