Re: [Bug 12832] New: kernel leaks a lot of memory

[Wu Fengguang <fengguang.wu@intel.com>]

Hi Pierre,

On Wed, Mar 11, 2009 at 09:57:38AM +0200, Pierre Ossman wrote:
> On Wed, 11 Mar 2009 15:36:19 +0800
> Wu Fengguang <fengguang.wu@intel.com> wrote:
> 
> > 
> > A quick question: are there any possibility of ftrace memory reservation?
> > 
> 
> You tell me. CONFIG_FTRACE was always disabled, but CONFIG_HAVE_*FTRACE
> is always on. FTRACE wasn't included in 2.6.26 though, and the bisect
> showed only ftrace commits. So it would explain things.

I worked up a simple debugging patch. Since the missing pages are
continuously spanned, several stack dumping shall be enough to catch
the page consumer.

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 27b8681..c0df7fd 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1087,6 +1087,13 @@ again:
 			goto failed;
 	}
 
+	/* wfg - hunting the 40000 missing pages */
+	{
+		unsigned long pfn = page_to_pfn(page);
+		if (pfn > 0x1000 && (pfn & 0xfff) <= 1)
+			dump_stack();
+	}
+
 	__count_zone_vm_events(PGALLOC, zone, 1 << order);
 	zone_statistics(preferred_zone, zone);
 	local_irq_restore(flags);

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