[PATCH #2] OOM kill trigger

[PATCH #2] OOM kill trigger

[Rik van Riel]

Hi,

As Hugh pointed out, the info on how many pages we have in the
swap cache is (of course) present in the swapper_space structure.

Patch has been shrunk accordingly...

Rik
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--- linux-2.4.6/mm/oom_kill.c.orig	Fri Jul  6 17:32:58 2001
+++ linux-2.4.6/mm/oom_kill.c	Fri Jul  6 19:19:25 2001
@@ -191,11 +191,28 @@
  */
 int out_of_memory(void)
 {
+	long cache_mem, limit;
+
 	/* Enough free memory?  Not OOM. */
 	if (nr_free_pages() > freepages.min)
 		return 0;

 	if (nr_free_pages() + nr_inactive_clean_pages() > freepages.low)
+		return 0;
+
+	/*
+	 * If the buffer and page cache (excluding swap cache) are over
+	 * their (/proc tunable) minimum, we're still not OOM.  We test
+	 * this to make sure we don't return OOM when the system simply
+	 * has a hard time with the cache.
+	 */
+	cache_mem = atomic_read(&page_cache_size);
+	cache_mem += atomic_read(&buffermem_pages);
+	cache_mem -= swapper_space.nrpages;
+	limit = (page_cache.min_percent + buffer_mem.min_percent);
+	limit *= num_physpages / 100;
+
+	if (cache_mem > limit)
 		return 0;

 	/* Enough swap space left?  Not OOM. */

Re: [PATCH #2] OOM kill trigger

[Jeff Garzik]

Rik van Riel wrote:
> +       cache_mem = atomic_read(&page_cache_size);
> +       cache_mem += atomic_read(&buffermem_pages);
> +       cache_mem -= swapper_space.nrpages;
> +       limit = (page_cache.min_percent + buffer_mem.min_percent);

Don't you need extra protection around swapper_space.nrpages?  A barrier
right above it?

-- 
Jeff Garzik      | A recent study has shown that too much soup
Building 1024    | can cause malaise in laboratory mice.
MandrakeSoft     |

Re: [PATCH #2] OOM kill trigger

[Rik van Riel]

On Fri, 6 Jul 2001, Jeff Garzik wrote:
> Rik van Riel wrote:
> > +       cache_mem = atomic_read(&page_cache_size);
> > +       cache_mem += atomic_read(&buffermem_pages);
> > +       cache_mem -= swapper_space.nrpages;
> > +       limit = (page_cache.min_percent + buffer_mem.min_percent);
>
> Don't you need extra protection around swapper_space.nrpages?
> A barrier right above it?

No. It's just a heuristic.

Besides, all that could change is the VALUE of
swapper_space.nrpages and it won't change by all
that much...

Rik
--
Executive summary of a recent Microsoft press release:
   "we are concerned about the GNU General Public License (GPL)"


		http://www.surriel.com/
http://www.conectiva.com/	http://distro.conectiva.com/