On Fri, 2 Apr 2010 17:02:43 +0100
Mel Gorman <mel@xxxxxxxxx> wrote:
> This patch adds a proc file /proc/sys/vm/compact_memory. When an arbitrary
> value is written to the file,
Might be better if "when the number 1 is written...". That permits you
to add 2, 3 and 4 later on.
> all zones are compacted. The expected user
> of such a trigger is a job scheduler that prepares the system before the
> target application runs.
>
Ick. The days of multi-user computers seems to have passed.
> ...
>
> +/* Compact all zones within a node */
> +static int compact_node(int nid)
> +{
> + int zoneid;
> + pg_data_t *pgdat;
> + struct zone *zone;
> +
> + if (nid < 0 || nid >= nr_node_ids || !node_online(nid))
> + return -EINVAL;
> + pgdat = NODE_DATA(nid);
> +
> + /* Flush pending updates to the LRU lists */
> + lru_add_drain_all();
> +
> + for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) {
> + struct compact_control cc;
> +
> + zone = &pgdat->node_zones[zoneid];
> + if (!populated_zone(zone))
> + continue;
> +
> + cc.nr_freepages = 0;
> + cc.nr_migratepages = 0;
> + cc.zone = zone;
It would be better to do
struct compact_control cc = {
.nr_freepages = 0,
etc
because if you later add more fields to compact_control, everything
else works by magick. That's served us pretty well with
writeback_control, scan_control, etc.
> + INIT_LIST_HEAD(&cc.freepages);
> + INIT_LIST_HEAD(&cc.migratepages);
> +
> + compact_zone(zone, &cc);
> +
> + VM_BUG_ON(!list_empty(&cc.freepages));
> + VM_BUG_ON(!list_empty(&cc.migratepages));
> + }
> +
> + return 0;
> +}
> +
> +/* Compact all nodes in the system */
> +static int compact_nodes(void)
> +{
> + int nid;
> +
> + for_each_online_node(nid)
> + compact_node(nid);
What if a node goes offline?
> + return COMPACT_COMPLETE;
> +}
> +
>
> ...
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