On Wed, 11 Mar 2009 15:14:45 +0800
Wu Fengguang <fengguang.wu@intel.com> wrote:

> On Wed, Mar 11, 2009 at 08:57:03AM +0200, Pierre Ossman wrote:
> > On Wed, 11 Mar 2009 09:37:40 +0800
> > Wu Fengguang <fengguang.wu@intel.com> wrote:
> > 
> > > 
> > > This 80MB noflags pages together with the below 80MB lru pages are
> > > very close to the missing page numbers :-) Could you run the following
> > > commands on fresh booted 2.6.27 and post the output files? Thank you!
> > > 
> > >         dd if=/dev/zero of=/tmp/s bs=1M count=1 seek=1024
> > >         cp /tmp/s /dev/null
> > > 
> > >         ./page-flags > flags
> > >         ./page-areas =0x20000 > areas-noflags
> > >         ./page-areas =0x00020 > areas-lru
> > > 
> > 
> > Attached.
> 
> Thank you very much!
> 
> > I have to say, the patterns look very much like some kind of leak.
> 
> Wow it looks really interesting.  The lru pages and noflags pages make
> perfect 1-page interleaved pattern...
> 

Another breakthrough. I turned off everything in kernel/trace, and now
the missing memory is back. Here's the relevant diff against the
original .config:

@@ -3677,18 +3639,15 @@
 # CONFIG_BACKTRACE_SELF_TEST is not set
 # CONFIG_LKDTM is not set
 # CONFIG_FAULT_INJECTION is not set
-CONFIG_LATENCYTOP=y
+# CONFIG_LATENCYTOP is not set
 # CONFIG_SYSCTL_SYSCALL_CHECK is not set
 CONFIG_HAVE_FTRACE=y
 CONFIG_HAVE_DYNAMIC_FTRACE=y
-CONFIG_TRACER_MAX_TRACE=y
-CONFIG_TRACING=y
 # CONFIG_FTRACE is not set
-CONFIG_IRQSOFF_TRACER=y
-CONFIG_SYSPROF_TRACER=y
-CONFIG_SCHED_TRACER=y
-CONFIG_CONTEXT_SWITCH_TRACER=y
-# CONFIG_FTRACE_STARTUP_TEST is not set
+# CONFIG_IRQSOFF_TRACER is not set
+# CONFIG_SYSPROF_TRACER is not set
+# CONFIG_SCHED_TRACER is not set
+# CONFIG_CONTEXT_SWITCH_TRACER is not set

I'll enable them one at a time and see when the bug reappears, but if
you have some ideas on which it could be, that would be helpful. The
machine takes some time to recompile a kernel. :)

Rgds
-- 
     -- Pierre Ossman

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