linux-kernel - Re: [GIT PULL] printk for 5.10 (includes lockless ringbuffer)

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Date:   Wed, 14 Oct 2020 17:07:41 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Rasmus Villemoes <linux@...musvillemoes.dk>
Cc:     Petr Mladek <pmladek@...e.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        John Ogness <john.ogness@...utronix.de>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Daniel Thompson <daniel.thompson@...aro.org>
Subject: Re: [GIT PULL] printk for 5.10 (includes lockless ringbuffer)

Hi Rasmus,

On Wed, Oct 14, 2020 at 4:58 PM Rasmus Villemoes
<linux@...musvillemoes.dk> wrote:
> On 14/10/2020 16.16, Geert Uytterhoeven wrote:
> > On Mon, Oct 12, 2020 at 4:50 PM Petr Mladek <pmladek@...e.com> wrote:
> >> - Fully lockless ringbuffer implementation, including the support for
> >>   continuous lines. It will allow to store and read messages in any
> >>   situation wihtout the risk of deadlocks and without the need
> >>   of temporary per-CPU buffers.
> >
> >     linux-m68k-atari_defconfig$ bloat-o-meter vmlinux.old
> > vmlinux.lockless_ringbuffer
> >     add/remove: 39/16 grow/shrink: 9/15 up/down: 214075/-4362 (209713)
> >     Function                                     old     new   delta
> >     _printk_rb_static_infos                        -  180224 +180224
> >     _printk_rb_static_descs                        -   24576  +24576
> >     [...]
> >
> > Seriously?!? Or am I being misled by the tools?
> >
> >     linux-m68k-atari_defconfig$ size vmlinux.old vmlinux.lockless_ringbuffer
> >        text    data     bss     dec     hex filename
> >     3559108 941716 177772 4678596 4763c4 vmlinux.old
> >     3563922 1152496 175276 4891694 4aa42e vmlinux.lockless_ringbuffer
> >
> > Apparently not...
>
> Hm, that's quite a lot. And the only reason the buffers don't live
> entirely in .bss is because a few of their entries have non-zero
> initializers.

Even if this would live in BSS, it would still consume 200 KiB of RAM.
Or am I missing something?

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds