lkml.org 
[lkml]   [2008]   [Mar]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH rc5-mm1 1/3] mm-have-zonelist: fix memcg ooms
On (11/03/08 21:12), Hugh Dickins didst pronounce:
> Memcgroups up against their limit were OOMing unjustifiably on x86_32
> with highmem: pages ripe for freeing were not being found.
>
> It's because the zonelist changes in vmscan.c now derive zone from gfp_mask,
> and the gfp mask being passed into try_to_free_mem_cgroup_pages is atuned
> to allocating a struct page_cgroup (__GFP_HIGHMEM masked off), whereas here
> we need to be scanning highmem zones.
>
> Frankenstein a gfp_mask from GFP_HIGHUSER_MOVABLE and the mask passed in.
>

Well spotted, but I have one query below.

> Signed-off-by: Hugh Dickins <hugh@veritas.com>
> ---
> Same error was in -rc3-mm1, sorry for not sending fix in time for -rc5-mm1.
> The error comes 1 or 4 patches earlier, but this patch atop 2.6.25-rc5-mm1
> fits best just after
> mm-have-zonelist-contains-structs-with-both-a-zone-pointer-and-zone_idx.patch
>
> I've other GFP masking fixes or cleanups to come another day: this fixes
> just one clear bug, peculiar to the -mm tree, orthogonal to the rest.
> But two little do_try_to_free_pages cleanups follow on from this...
>
> mm/vmscan.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> --- 2.6.25-rc5-mm1/mm/vmscan.c 2008-03-11 14:19:36.000000000 +0000
> +++ linux/mm/vmscan.c 2008-03-11 20:09:05.000000000 +0000
> @@ -1444,7 +1444,6 @@ unsigned long try_to_free_mem_cgroup_pag
> gfp_t gfp_mask)
> {
> struct scan_control sc = {
> - .gfp_mask = gfp_mask,
> .may_writepage = !laptop_mode,
> .may_swap = 1,
> .swap_cluster_max = SWAP_CLUSTER_MAX,
> @@ -1454,9 +1453,10 @@ unsigned long try_to_free_mem_cgroup_pag
> .isolate_pages = mem_cgroup_isolate_pages,
> };
> struct zonelist *zonelist;
> - int target_zone = gfp_zonelist(GFP_HIGHUSER_MOVABLE);
>
> - zonelist = &NODE_DATA(numa_node_id())->node_zonelists[target_zone];
> + sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
> + (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
> + zonelist = NODE_DATA(numa_node_id())->node_zonelists;

While it is clear you are setting the mask to include HIGHMEM-related flags,
it's not as clear to me why you alter the zonelist as well. target_zone was
already based on HIGHMEM so what are you fixing there?

It should still work as ->node_zonelists[0] is a zonelist suitable for node
fallback as opposed to node_zonelists[1] which is for GFP_THISNODE but
maybe this was not quite what you intended?

Probably something obvious that will hit me the second I push send :)

> if (do_try_to_free_pages(zonelist, sc.gfp_mask, &sc))
> return 1;
> return 0;
>

--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab


\
 
 \ /
  Last update: 2008-03-12 13:31    [from the cache]
©2003-2011 Jasper Spaans