linux-kernel - Re: [PATCH 0/4] printk_index: Fix false positives

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Date: Thu, 29 Feb 2024 08:37:55 +0800
From: Xiubo Li <xiubli@...hat.com>
To: Geert Uytterhoeven <geert+renesas@...der.be>,
 Chris Down <chris@...isdown.name>, Petr Mladek <pmladek@...e.com>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
 Jessica Yu <jeyu@...nel.org>, Steven Rostedt <rostedt@...dmis.org>,
 John Ogness <john.ogness@...utronix.de>,
 Sergey Senozhatsky <senozhatsky@...omium.org>,
 Jason Baron <jbaron@...mai.com>, Jim Cromie <jim.cromie@...il.com>,
 Ilya Dryomov <idryomov@...il.com>, Jeff Layton <jlayton@...nel.org>
Cc: linux-kernel@...r.kernel.org, ceph-devel@...r.kernel.org
Subject: Re: [PATCH 0/4] printk_index: Fix false positives


On 2/28/24 22:00, Geert Uytterhoeven wrote:
> 	Hi all,
>
> When printk-indexing is enabled, each printk() invocation emits a
> pi_entry structure, containing the format string and other information
> related to its location in the kernel sources.  This is even true when
> the printk() is protected by an always-false check, as is typically the
> case for debug messages: while the actual code to print the message is
> optimized out by the compiler, the pi_entry structure is still emitted.
> Hence when debugging is disabled, this leads to the inclusion in the
> index of lots of printk formats that cannot be emitted by the current
> kernel.
>
> This series fixes that for the common debug helpers under include/.
> It reduces the size of an arm64 defconfig kernel with
> CONFIG_PRINTK_INDEX=y by ca. 1.5 MiB, or 28% of the overhead of
> enabling CONFIG_PRINTK_INDEX=y.
>
> Notes:
>    - netdev_(v)dbg() and netif_(v)dbg() are not affected, as
>      net{dev,if}_printk() do not implement printk-indexing, except
>      for the single global internal instance of __netdev_printk().
>    - This series fixes only debug code in global header files under
>      include/.  There are more cases to fix in subsystem-specific header
>      files and in sources files.
>
> Thanks for your comments!
>
> Geert Uytterhoeven (4):
>    printk: Let no_printk() use _printk()
>    dev_printk: Add and use dev_no_printk()
>    dyndbg: Use *no_printk() helpers
>    ceph: Use no_printk() helper
>
>   include/linux/ceph/ceph_debug.h | 18 +++++++-----------
>   include/linux/dev_printk.h      | 25 +++++++++++++------------
>   include/linux/dynamic_debug.h   |  4 ++--
>   include/linux/printk.h          |  2 +-
>   4 files changed, 23 insertions(+), 26 deletions(-)
>
This series LGTM.

Reviewed-by: Xiubo Li <xiubli@...hat.com>