linux-kernel - Re: [RFC PATCH 25/26] UBIFS: add debugging stuff

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Date:	Tue, 1 Apr 2008 12:00:39 +0300
From:	"Pekka Enberg" <penberg@...helsinki.fi>
To:	Artem.Bityutskiy@...ia.com
Cc:	"Artem Bityutskiy" <dedekind@...dex.ru>,
	LKML <linux-kernel@...r.kernel.org>,
	"Adrian Hunter" <ext-adrian.hunter@...ia.com>
Subject: Re: [RFC PATCH 25/26] UBIFS: add debugging stuff

Hi Artem,

On Tue, Apr 1, 2008 at 11:32 AM, Artem Bityutskiy
<Artem.Bityutskiy@...ia.com> wrote:
>  I am not sure what you mean. I would not want to delve into a general
>  discussion of the debugging stuff. I would better talk about specific
>  things. I'll just point you examples of debugging stuff in the kernel
>  in other subsystems which exists and does not hurt anyone. And I believe
>  it is helpful. It is compiled out by default and is enable when it is
>  needed to hunt a bug.
>
>  fs/ext2: ea_idebug(), EXT2FS_DEBUG
>  fs/xfs: #ifdef DEBUG, XFS_LOUD_RECOVERY and so on
>  fs/ocfs2: OCFS2_DEBUG_FS
>  fs/jfs: CONFIG_JFS_DEBUG, assert(), etc
>  fs: DEBUG_EPOLL, #ifdef DEBUG
>  fs/jbd2: assert_spin_locked(), CONFIG_JBD2_DEBUG, etc
>  mm: CONFIG_SLUB_DEBUG, SLABDEBUG, CONFIG_DEBUG_VM, and so on

But they're totally different kind of thing! They're not for disabling
hundreds of debug-only printks sprinkled around the kernel. Instead,
they let you disable well-defined debugging checks for kernel speed
and/or size optimizations. And btw, CONFIG_SLUB_DEBUG is only a kernel
size optimization for CONFIG_EMBEDDED. The SLUB debugging code can be
turned on and off at run-time.

                       Pekka
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