On Wed, Jan 22, 2014 at 01:57:14AM -0500, Johannes Weiner wrote:
> Not at this time, I'll try to look into that. For now, I am updating
> the patch to revert the shrinker back to DEFAULT_SEEKS and change the
> object count to only include objects above a certain threshold, which
> assumes a worst-case population of 4 in 64 slots. It's not perfect,
> but neither was the seeks magic, and it's easier to reason about what
> it's actually doing.
Ah, the quality of 2am submissions... 8 out of 64 of course.
> @@ -266,14 +269,38 @@ struct list_lru workingset_shadow_nodes;
> static unsigned long count_shadow_nodes(struct shrinker *shrinker,
> struct shrink_control *sc)
> {
> - return list_lru_count_node(&workingset_shadow_nodes, sc->nid);
> + unsigned long shadow_nodes;
> + unsigned long max_nodes;
> + unsigned long pages;
> +
> + shadow_nodes = list_lru_count_node(&workingset_shadow_nodes, sc->nid);
> + pages = node_present_pages(sc->nid);
> + /*
> + * Active cache pages are limited to 50% of memory, and shadow
> + * entries that represent a refault distance bigger than that
> + * do not have any effect. Limit the number of shadow nodes
> + * such that shadow entries do not exceed the number of active
> + * cache pages, assuming a worst-case node population density
> + * of 1/16th on average.
1/8th. The actual code is consistent:
> + * On 64-bit with 7 radix_tree_nodes per page and 64 slots
> + * each, this will reclaim shadow entries when they consume
> + * ~2% of available memory:
> + *
> + * PAGE_SIZE / radix_tree_nodes / node_entries / PAGE_SIZE
> + */
> + max_nodes = pages >> (1 + RADIX_TREE_MAP_SHIFT - 3);
> +
> + if (shadow_nodes <= max_nodes)
> + return 0;
> +
> + return shadow_nodes - max_nodes;
> }
>
> static enum lru_status shadow_lru_isolate(struct list_head *item,
> spinlock_t *lru_lock,
> void *arg)
> {
> - unsigned long *nr_reclaimed = arg;
> struct address_space *mapping;
> struct radix_tree_node *node;
> unsigned int i;
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