lkml.org 
[lkml]   [2003]   [Oct]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: Strange dcache memory pressure when highmem enabled
On Tue, Oct 14, 2003 at 10:43:52PM -0700, Andrew Morton wrote:
> Neil Brown <neilb@cse.unsw.edu.au> wrote:
> >
> > I noticed that shrink_caches calls shrink_dcache_memory independant
> > of the classzone that is being shrunk. So if we are trying to
> > shrink ZONE_HIGHMEM, the dentry_cache is shrunk, even though the
> > dentry_cache doesn't live in highmem. However I'm not sure if I have
> > understood the classzones well enough for that observation even to
> > make sense.
>
> Makes heaps of sense. Here's an instabackport of what we did in 2.6:
>
> mm/vmscan.c | 12 +++++++++---
> 1 files changed, 9 insertions(+), 3 deletions(-)
>
> diff -puN mm/vmscan.c~a mm/vmscan.c
> --- 24/mm/vmscan.c~a 2003-10-14 22:41:34.000000000 -0700
> +++ 24-akpm/mm/vmscan.c 2003-10-14 22:42:22.000000000 -0700
> @@ -640,11 +640,17 @@ int try_to_free_pages_zone(zone_t *class
> nr_pages = shrink_caches(classzone, gfp_mask, nr_pages, &failed_swapout);
> if (nr_pages <= 0)
> return 1;
> - shrink_dcache_memory(vm_vfs_scan_ratio, gfp_mask);
> - shrink_icache_memory(vm_vfs_scan_ratio, gfp_mask);
> + if (classzone - classzone->zone_pgdat->node_zones <
> + ZONE_HIGHMEM) {
> + shrink_dcache_memory(vm_vfs_scan_ratio,
> + gfp_mask);
> + shrink_icache_memory(vm_vfs_scan_ratio,
> + gfp_mask);
> #ifdef CONFIG_QUOTA
> - shrink_dqcache_memory(vm_vfs_scan_ratio, gfp_mask);
> + shrink_dqcache_memory(vm_vfs_scan_ratio,
> + gfp_mask);
> #endif
> + }
> if (!failed_swapout)
> failed_swapout = !swap_out(classzone);
> } while (--tries);

An highmem user can make use of lowmem too. Think a 1G box, it looks
wrong to disallow highmem to shrink the 800M of dcache in the normal/dma
zones.

I wonder if what he's suffering from is a reduced normal zone due the
mem_map_t being larger. The reduced normal zone will trigger the dcache
shrinking more frequently. But he may want to try again with 2.4.23pre7
with a classzone aware refill_inactive that will ensure the inactive
list has enough lowmem pages before shrink_caches claims failure.

Andrea - If you prefer relying on open source software, check these links:
rsync.kernel.org::pub/scm/linux/kernel/bkcvs/linux-2.[45]/
http://www.cobite.com/cvsps/
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 13:55    [from the cache]
©2003-2014 Jasper Spaans. Advertise on this site