linux-kernel - Re: Major slab mem leak with 2.6.17 / GCC 4.1.1

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Message-Id: <1160991215.17131.26.camel@Homer.simpson.net>
Date:	Mon, 16 Oct 2006 09:33:35 +0000
From:	Mike Galbraith <efault@....de>
To:	Catalin Marinas <catalin.marinas@...il.com>
Cc:	Pekka Enberg <penberg@...helsinki.fi>,
	"nmeyers@...tmark.com" <nmeyers@...tmark.com>,
	linux-kernel@...r.kernel.org
Subject: Re: Major slab mem leak with 2.6.17 / GCC 4.1.1

On Mon, 2006-10-16 at 09:44 +0100, Catalin Marinas wrote:
> On 16/10/06, Mike Galbraith <efault@....de> wrote:
> > On Mon, 2006-10-16 at 09:07 +0100, Catalin Marinas wrote:
> > > Kmemleak introduces some overhead but shouldn't be that bad.
> > > DEBUG_SLAB also introduces an overhead by erasing the data in the
> > > allocated blocks.
> >
> > 2.6.18 with your rc6 patch booted normally with stack unwind enabled.
> 
> The only difference is that kmemleak now uses save_stack_trace() to
> generate the call chain. In the previous versions I implemented a
> simple stack backtrace myself, with the disadvantage that it only
> worked on ARM and x86.
> 
> I think kmemleak should use the common stack trace API and investigate
> why it is slower (either save_stack_trace is slower with stack unwind
> enabled or kmemleak doesn't use these functions properly).

The stack traces look fine without unwind, and at a glance looked fine
with unwind as well, so I speculate you must be using save_stack_trace
properly.  The only difference I noticed was the incredible speed
difference.  I gave up on getting to run level 5 with unwind, getting to
level 2 took ages, and the box was horribly slow at everything.

	-Mike

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