Re: 2.6.0-test5/6 (and probably 7 too) size-4096 memory leak

[Andrew Morton <akpm@osdl.org>]

William Lee Irwin III <wli@holomorphy.com> wrote:
>
> Alberto Bertogli <albertogli@telpin.com.ar> wrote:
> >>  Slabinfo reports that size-4096 has 104341 active objects and growing.
> >>  On another box at home I see the same issue with test6, but "only" with
> >>  11612 objects; I'm not posting info on this box as I guess the mailserver
> >>  is much more important because the leak is really noticeable.
> 
> On Wed, Oct 15, 2003 at 09:19:18PM -0700, Andrew Morton wrote:
> > At least I'm not the only one; my main desktop machine does the same
> > thing.  It leaks two megabytes a day into size-4096, like clockwork.  It's
> > up to 43 megs now.
> > I was ignoring it and hoping it would go away.  Ho hum.  Tricky.
> 
> I immediately thought of bundling this in with the do_exit() BUG() and
> /proc/ oopsen, but we would see a task_t leak also in that case. I still
> say the /proc/ change is swiss cheese (well, in concept there's nothing
> wrong with what it wants to do, but there's something definitely wrong
> with the implementation since backing it out stops things from oopsing),
> but this looks unrelated therefore (which is actually depressing, since
> we can't kill all three in one shot and/or get anywhere by correlating).
> I should try using a dedicated stack slab to see if they're stacks even
> though task_t's aren't leaking.
> 

This leak is at least a couple of months old.

The recent (test7) /proc oops was fixed when Linus reverted the
job-control-in-signal-struct patch.

This leak is of size-4096: it isn't kernel stacks.

I did a quicky audit of all kmalloc(PAGE_SIZE) instances and everything
looked OK: one suspect in the NFS server but I wasn't able to force
speedier bloat by exercising the NFS server in my normal usage pattern.

I'm thinking we need to stuff builtin_return_address(0) into the object and
write a dumper, but I haven't looked into that.  Maybe I can persuade
Manfred to cook up a custom patch to do that?  Just for size-4096?  Something
really crude will be fine.