Messages in this thread Patch in this message | | | Date | Thu, 3 Jul 2008 18:39:03 +0100 | From | Mel Gorman <> | Subject | Re: [Bug #10961] 2.6.26-rc: nfsd hangs for a few sec |
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On (01/07/08 18:04), Alexander Beregalov didst pronounce: > 2008/7/1 Mel Gorman <mel@csn.ul.ie>: > > I still have no useful reaction to this. According to Christoph Hellwig, > > this lockup has been appearing since lockdep was introduced but for some > > reason is easier to trigger now. It bisected to the two-zonelist changes > > but it still looks like a red herring as I cannot see how reclaim has > > changed significantly as a result of that patch. > > Do you wait reaction from me? Can I help? > As I mentioned, the lockup does not happen when lockdep is disabled. >
Sorry for the slow response Alexander.
This bug is likely fixed by commit 494de90098784b8e2797598cefdd34188884ec2e which will be visible publicly later when maintenance on master.kernel.org finishes. I included it below for convenience.
The lockdep warning still exists but it is a false positive and should be relatively hard to trigger again. It would be nice to have confirmation of this.
commit 494de90098784b8e2797598cefdd34188884ec2e Author: Mel Gorman <mel@csn.ul.ie> Date: Thu Jul 3 05:27:51 2008 +0100
Do not overwrite nr_zones on !NUMA when initialising zlcache_ptr The non-NUMA case of build_zonelist_cache() would initialize the zlcache_ptr for both node_zonelists[] to NULL. Which is problematic, since non-NUMA only has a single node_zonelists[] entry, and trying to zero the non-existent second one just overwrote the nr_zones field instead. As kswapd uses this value to determine what reclaim work is necessary, the result is that kswapd never reclaims. This causes processes to stall frequently in low-memory situations as they always direct reclaim. This patch initialises zlcache_ptr correctly. Signed-off-by: Mel Gorman <mel@csn.ul.ie> Tested-by: Dan Williams <dan.j.williams@intel.com> [ Simplified patch a bit ] Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> --- mm/page_alloc.c | 1 - 1 files changed, 0 insertions(+), 1 deletions(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 2f55295..f32fae3 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -2328,7 +2328,6 @@ static void build_zonelists(pg_data_t *pgdat) static void build_zonelist_cache(pg_data_t *pgdat) { pgdat->node_zonelists[0].zlcache_ptr = NULL; - pgdat->node_zonelists[1].zlcache_ptr = NULL; } #endif /* CONFIG_NUMA */
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