Re: Memory and rsync problem with vanilla 2.6.7

[Nick Piggin]

Linus Torvalds wrote:
> On Sat, 19 Jun 2004, Grzegorz Kulewski wrote:
>
> > Is this bug or feature? Is there some wreid memmory leak? Where is my RAM?
>
>
> Your memory is apparently in dentry and inode memory:
>
> 	ext3_inode_cache   62553  62553   4096		(244MB)
> 	dentry_cache       48768  48768   4096		(190MB)
>
> and it really looks like you have enabled CONFIG_DEBUG_PAGEALLOC, which 
> just eats memory like mad (a dentry is normally ~200 bytes, but then when 
> it is rounded up to page-size, it takes 20 times the memory).
>
> So don't enable DEBUG_PAGEALLOC unless you really want to debug some 
> strange problem.

This could be it. But can you check whether your previous well-behaving
kernel also has CONFIG_DEBUG_PAGEALLOC on? If so, then it is possible
that VM behaviour has regressed.

Of course, DEBUG_PAGEALLOC is the wrong target to attempt to tune for:
without it, those above two items would take up a combined 40 megs.

> That said, there might be a memory balancing problem too, and
> DEBUG_PAGEALLOC just makes it more obvious.  Nick Piggin reports that an
> "obvious fix" by Andrew potentially causes problems, and if you're a BK
> user, you could try just backing out this cset:
>
> 	ChangeSet@xxxxxxxxxxx, 2004-06-03 07:58:03-07:00, akpm@xxxxxxxx
> 	  [PATCH] shrink_all_memory() fixes
>
> 	....
>
> (check with "bk changes" what the revision is in your tree, and do a
>
> 	bk cset -xX.XXX.XX.X
>
> to try reverting it. Quite possibly that fix makes the VM much less likely
> to throw out the VM caches, which would make the debug problem much 
> worse).

Well it doesn't seem to have caused too much trouble as yet... But it
is the obvious candidate if your problems continue. If you are not a
bk user, the attached patch will also revert that change.
 linux-2.6-npiggin/mm/vmscan.c |    7 ++-----
 1 files changed, 2 insertions(+), 5 deletions(-)

diff -puN mm/vmscan.c~vm-revert-fix mm/vmscan.c
--- linux-2.6/mm/vmscan.c~vm-revert-fix	2004-06-12 16:53:02.000000000 +1000
+++ linux-2.6-npiggin/mm/vmscan.c	2004-06-12 16:54:26.000000000 +1000
@@ -813,9 +813,8 @@ shrink_caches(struct zone **zones, int p
 		struct zone *zone = zones[i];
 		int max_scan;
 
-		zone->temp_priority = priority;
-		if (zone->prev_priority > priority)
-			zone->prev_priority = priority;
+		if (zone->free_pages < zone->pages_high)
+			zone->temp_priority = priority;
 
 		if (zone->all_unreclaimable && priority != DEF_PRIORITY)
 			continue;	/* Let kswapd poll it */
@@ -996,8 +995,6 @@ scan:
 					all_zones_ok = 0;
 			}
 			zone->temp_priority = priority;
-			if (zone->prev_priority > priority)
-				zone->prev_priority = priority;
 			max_scan = (zone->nr_active + zone->nr_inactive)
 								>> priority;
 			reclaimed = shrink_zone(zone, max_scan, GFP_KERNEL,

_