From: Mel Gorman <mel@csn.ul.ie>
To: Andrea Arcangeli <aarcange@redhat.com>
Cc: Shaohua Li <shaohua.li@intel.com>,
Andrew Morton <akpm@linux-foundation.org>,
linux-mm <linux-mm@kvack.org>,
"Chen, Tim C" <tim.c.chen@intel.com>
Subject: Re: too big min_free_kbytes
Date: Wed, 26 Jan 2011 17:42:37 +0000 [thread overview]
Message-ID: <20110126174236.GV18984@csn.ul.ie> (raw)
In-Reply-To: <20110126163655.GU18984@csn.ul.ie>
On Wed, Jan 26, 2011 at 04:36:55PM +0000, Mel Gorman wrote:
> > But the wmarks don't
> > seem the real offender, maybe it's something related to the tiny pci32
> > zone that materialize on 4g systems that relocate some little memory
> > over 4g to make space for the pci32 mmio. I didn't yet finish to debug
> > it.
> >
>
> This has to be it. What I think is happening is that we're in balance_pgdat(),
> the "Normal" zone is never hitting the watermark and we constantly call
> "goto loop_again" trying to "rebalance" all zones.
>
Confirmed. The following "patch" should fix allow the number of free pages to
drop to a sensible level. Note, this is not intended as a fix because it's
the utterly wrong approach to take. It's only to illustrate where things
are going wrong when the top-most zone is very small.
diff --git a/mm/vmscan.c b/mm/vmscan.c
index f5d90de..477cb77 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2259,7 +2259,8 @@ static bool sleeping_prematurely(pg_data_t *pgdat, int order, long remaining,
}
if (!zone_watermark_ok_safe(zone, order, high_wmark_pages(zone),
- classzone_idx, 0))
+ classzone_idx, 0) &&
+ zone->present_pages >= pgdat->node_present_pages >> 2)
all_zones_ok = false;
else
balanced += zone->present_pages;
@@ -2446,15 +2447,18 @@ loop_again:
if (!zone_watermark_ok_safe(zone, order,
high_wmark_pages(zone), end_zone, 0)) {
- all_zones_ok = 0;
- /*
- * We are still under min water mark. This
- * means that we have a GFP_ATOMIC allocation
- * failure risk. Hurry up!
- */
- if (!zone_watermark_ok_safe(zone, order,
- min_wmark_pages(zone), end_zone, 0))
- has_under_min_watermark_zone = 1;
+ if (zone->present_pages >= pgdat->node_present_pages >> 2) {
+ all_zones_ok = 0;
+
+ /*
+ * We are still under min water mark. This
+ * means that we have a GFP_ATOMIC allocation
+ * failure risk. Hurry up!
+ */
+ if (!zone_watermark_ok_safe(zone, order,
+ min_wmark_pages(zone), end_zone, 0))
+ has_under_min_watermark_zone = 1;
+ }
} else {
/*
* If a zone reaches its high watermark,
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next prev parent reply other threads:[~2011-01-26 17:43 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-01-24 3:56 too big min_free_kbytes Shaohua Li
2011-01-24 15:00 ` Andrea Arcangeli
2011-01-25 14:35 ` Mel Gorman
2011-01-26 14:17 ` Mel Gorman
2011-01-26 15:23 ` Mel Gorman
2011-01-26 15:42 ` Andrea Arcangeli
2011-01-26 16:36 ` Mel Gorman
2011-01-26 17:42 ` Mel Gorman [this message]
2011-01-27 13:40 ` Mel Gorman
2011-01-27 15:27 ` Andrea Arcangeli
2011-01-27 16:03 ` Mel Gorman
2011-01-27 18:52 ` Andrea Arcangeli
2011-01-27 20:33 ` Rik van Riel
2011-01-27 21:31 ` Mel Gorman
2011-01-27 23:18 ` Rik van Riel
2011-01-28 10:35 ` Mel Gorman
2011-01-28 16:28 ` Andrea Arcangeli
2011-01-28 16:46 ` Mel Gorman
2011-01-28 17:16 ` Rik van Riel
2011-01-28 17:46 ` Andrea Arcangeli
2011-01-28 18:03 ` Rik van Riel
2011-01-28 18:24 ` Andrea Arcangeli
2011-01-28 19:34 ` Rik van Riel
2011-01-28 19:45 ` Andrea Arcangeli
2011-01-28 20:55 ` Rik van Riel
2011-01-29 19:45 ` Andrea Arcangeli
2011-01-28 17:34 ` Andrea Arcangeli
2011-01-28 17:10 ` Rik van Riel
2011-02-03 2:58 ` Andrea Arcangeli
2011-02-03 13:15 ` Mel Gorman
2011-02-03 18:59 ` Andrea Arcangeli
2011-02-03 14:36 ` Rik van Riel
2011-02-03 19:11 ` Andrea Arcangeli
2011-02-12 1:28 ` Simon Kirby
2011-02-14 2:25 ` Shaohua Li
2011-02-22 14:25 ` Mel Gorman
2011-02-22 14:42 ` Andrea Arcangeli
2011-02-22 14:50 ` Mel Gorman
2011-02-22 14:54 ` Andrea Arcangeli
2011-02-22 16:04 ` Mel Gorman
2011-02-22 16:40 ` Rik van Riel
2011-02-23 5:29 ` Shaohua Li
2011-02-23 14:45 ` Andrea Arcangeli
2011-02-24 8:08 ` Shaohua Li
2011-02-24 9:52 ` Mel Gorman
2011-02-24 9:57 ` Mel Gorman
2011-02-24 14:27 ` Andrea Arcangeli
2011-02-24 14:04 ` Andrea Arcangeli
2011-02-25 0:51 ` Shaohua Li
2011-02-25 12:13 ` Mel Gorman
2011-02-12 9:48 ` alex shi
2011-02-22 14:24 ` Mel Gorman
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