On Tue 09-04-13 14:13:12, Michal Hocko wrote:
[...]
> 2) kbuild test showed more or less the same results
> usage_in_bytes
> Base
> Group A Group B
> Median 394817536 395634688
>
> Patches applied
> median 483481600 302131200
>
> A is kept closer to the soft limit again. There is some fluctuation
> around the limit because kbuild creates a lot of short lived processes.
> Base: pgscan_kswapd_dma32 1648718 pgsteal_kswapd_dma32 1510749
> Patched: pgscan_kswapd_dma32 2042065 pgsteal_kswapd_dma32 1667745
OK, so I have patched the base version with the patch bellow which
uncovers soft reclaim scanning and reclaim and guess what:
Base: pgscan_kswapd_dma32 3710092 pgsteal_kswapd_dma32 3225191
Patched: pgscan_kswapd_dma32 1846700 pgsteal_kswapd_dma32 1442232
Base: pgscan_direct_dma32 2417683 pgsteal_direct_dma32 459702
Patched: pgscan_direct_dma32 1839331 pgsteal_direct_dma32 244338
The numbers are obviously timing dependent (wrt. previous run ~10% for
the patched kernel) but the ~1/2 half wrt. the base kernel seems real
we just haven't seen it previously because it wasn't accounted. I guess
this can be attributed to prio-0 soft reclaim behavior and a lot of
dirty pages on the LRU.
> The differences are much bigger now so it would be interesting how much
> has been scanned/reclaimed during soft reclaim in the base kernel.
---
>From 82761298527333eeecdf134b7426f95254b3e78c Mon Sep 17 00:00:00 2001
From: Michal Hocko <mhocko@xxxxxxx>
Date: Tue, 9 Apr 2013 15:46:53 +0200
Subject: [PATCH] account soft limit reclaim as it is part of the global
reclaim currently
---
mm/vmscan.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/mm/vmscan.c b/mm/vmscan.c
index df78d17..4dcc2ea 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -92,6 +92,7 @@ struct scan_control {
* are scanned.
*/
nodemask_t *nodemask;
+ bool soft_reclaim;
};
#define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
@@ -138,6 +139,10 @@ static bool global_reclaim(struct scan_control *sc)
{
return !sc->target_mem_cgroup;
}
+static bool soft_reclaim(struct scan_control *sc)
+{
+ return sc->soft_reclaim;
+}
#else
static bool global_reclaim(struct scan_control *sc)
{
@@ -1309,7 +1314,7 @@ shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec,
__mod_zone_page_state(zone, NR_LRU_BASE + lru, -nr_taken);
__mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken);
- if (global_reclaim(sc)) {
+ if (global_reclaim(sc) || soft_reclaim(sc)) {
zone->pages_scanned += nr_scanned;
if (current_is_kswapd())
__count_zone_vm_events(PGSCAN_KSWAPD, zone, nr_scanned);
@@ -1328,7 +1333,7 @@ shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec,
reclaim_stat->recent_scanned[file] += nr_taken;
- if (global_reclaim(sc)) {
+ if (global_reclaim(sc) || soft_reclaim(sc)) {
if (current_is_kswapd())
__count_zone_vm_events(PGSTEAL_KSWAPD, zone,
nr_reclaimed);
@@ -2401,6 +2406,7 @@ unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *memcg,
.order = 0,
.priority = 0,
.target_mem_cgroup = memcg,
+ .soft_reclaim = true,
};
struct lruvec *lruvec = mem_cgroup_zone_lruvec(zone, memcg);
--
1.7.10.4
--
Michal Hocko
SUSE Labs
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