Re: kernel 2.6.22: what IS the VM doing?

Rik van Riel
2007-09-05T16:24:41Z

[-- Attachment #1: Type: text/plain, Size: 754 bytes --]

Sami Farin wrote:
> On Tue, Sep 04, 2007 at 21:37:35 -0400, Rik van Riel wrote:
>> Is the system trying to evict pages like crazy when your
>> system becomes unusable?
>
> I think so..
>
>> If so, I wonder if kswapd is simply doing the wrong thing
>> and trying to evict data from all zones, simply because the
>> highmem zone is low on free pages...
>
> *shrug*

The attached patch should make sure kswapd does not free an
excessive number of pages in zone_normal just because the
pages in zone_highmem are difficult to free.

It does give kswapd a large margin to continue putting equal
pressure on all zones in normal situations.

Sami, could you try out this patch to see if it helps your
situation?

Signed-off-by: Rik van Riel <riel@redhat.com>

[-- Attachment #2: linux-2.6-excessive-pageout.patch --]
[-- Type: text/x-patch, Size: 714 bytes --]

--- linux-2.6.22.noarch/mm/vmscan.c.excessive 2007-09-05 12:19:49.000000000 -0400
+++ linux-2.6.22.noarch/mm/vmscan.c 2007-09-05 12:21:40.000000000 -0400
@@ -1371,7 +1371,13 @@ loop_again:
temp_priority[i] = priority;
sc.nr_scanned = 0;
note_zone_scanning_priority(zone, priority);
- nr_reclaimed += shrink_zone(priority, zone, &sc);
+ /*
+ * We put equal pressure on every zone, unless one
+ * zone has way too many pages free already.
+ */
+ if (!zone_watermark_ok(zone, order, 8*zone->pages_high,
+ end_zone, 0))
+ nr_reclaimed += shrink_zone(priority, zone, &sc);
reclaim_state->reclaimed_slab = 0;
nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL,
lru_pages);