Re: Large slab cache in 2.6.1

Chris Wedgwood
2004-02-22T05:44:21Z

On Sun, Feb 22, 2004 at 04:37:46PM +1100, Nick Piggin wrote:

> Can you upgrade to 2.6.3-mm2? It would be ideal if you could test
> this patch against that kernel due to the other VM changes.

Sure.

> Chris, could you test this too please? Thanks.

I tested this change to a stock 2.6.3 kernel and saw a marginally
better situation... 650MB in slab instead of 850MB:

===== page_alloc.c 1.186 vs edited =====
--- 1.186/mm/page_alloc.c Wed Feb 18 19:43:04 2004
+++ edited/page_alloc.c Sat Feb 21 21:05:32 2004
@@ -764,13 +764,18 @@

EXPORT_SYMBOL(nr_free_pages);

+/*
+ * return the number of non-highmem pages (we should probably rename
+ * this function? --cw)
+ */
unsigned int nr_used_zone_pages(void)
{
unsigned int pages = 0;
struct zone *zone;

for_each_zone(zone)
- pages += zone->nr_active + zone->nr_inactive;
+ if (!is_highmem(zone))
+ pages += zone->nr_active + zone->nr_inactive;

return pages;
}

I'll test -mm2 with your patch shortly.

>

> @@ -145,7 +145,7 @@ static int shrink_slab(unsigned long sca
> if (down_trylock(&shrinker_sem))
> return 0;
>
> - pages = nr_used_zone_pages();
> + pages = nr_lowmem_lru_pages();

Cool. I think renaming this i a good idea.

> -unsigned int nr_used_zone_pages(void)
> +unsigned int nr_lowmem_lru_pages(void)
> {
> + pg_data_t *pgdat;
> unsigned int pages = 0;
> - struct zone *zone;
>
> - for_each_zone(zone)
> - pages += zone->nr_active + zone->nr_inactive;
> + for_each_pgdat(pgdat) {
> + int i;
> + for (i = 0; i < ZONE_HIGHMEM; i++) {
> + struct zone *zone = pgdat->node_zones + i;
> + pages += zone->nr_active + zone->nr_inactive;
> + }
> + }

Why not just check is_highmem(zone) here?

> -extern unsigned int nr_used_zone_pages(void);
> +extern unsigned int nr_lowmem_lru_pages(void);

Since shrink_slab() is the only consumer of this why not move the
function to vmscan.c just above shrink_slab()?