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Message-ID: <20150430160044.GF5117@pd.tnic>
Date: Thu, 30 Apr 2015 18:00:44 +0200
From: Borislav Petkov <bp@...e.de>
To: "Luis R. Rodriguez" <mcgrof@...not-panic.com>
Cc: mingo@...e.hu, tglx@...utronix.de, hpa@...or.com,
plagnioj@...osoft.com, tomi.valkeinen@...com,
daniel.vetter@...el.com, airlied@...ux.ie, dledford@...hat.com,
awalls@...metrocast.net, syrjala@....fi, luto@...capital.net,
mst@...hat.com, cocci@...teme.lip6.fr,
linux-kernel@...r.kernel.org,
"Luis R. Rodriguez" <mcgrof@...e.com>,
Juergen Gross <jgross@...e.com>,
Daniel Vetter <daniel.vetter@...ll.ch>,
Dave Airlie <airlied@...hat.com>,
Bjorn Helgaas <bhelgaas@...gle.com>, x86@...nel.org
Subject: Re: [PATCH v4 2/8] init.h: add __read_mostly to early_param_on_off()
On Wed, Apr 29, 2015 at 02:44:21PM -0700, Luis R. Rodriguez wrote:
> From: "Luis R. Rodriguez" <mcgrof@...e.com>
So this one is missing a commit message too but we need to talk about
this. Why are we adding __read_mostly in the macro? This would put every
param declared this way into __section__(".data..read_mostly") and I'm
not really convinced that is needed.
Those setup params get accessed a couple of times only during boot, in
non-critical paths so we don't really care.
If you care about pat_enabled being read a lot, you could do:
int __read_mostly pat_enabled;
only for it.
But for every param declared this way? I'm not sure we want that...
> Cc: Andy Walls <awalls@...metrocast.net>
> Cc: Doug Ledford <dledford@...hat.com>
> Cc: Andy Lutomirski <luto@...capital.net>
> Cc: Ingo Molnar <mingo@...e.hu>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Juergen Gross <jgross@...e.com>
> Cc: Daniel Vetter <daniel.vetter@...ll.ch>
> Cc: Dave Airlie <airlied@...hat.com>
> Cc: Bjorn Helgaas <bhelgaas@...gle.com>
> Cc: Borislav Petkov <bp@...e.de>
> Cc: Michael S. Tsirkin <mst@...hat.com>
> Cc: linux-kernel@...r.kernel.org
> Cc: x86@...nel.org
> Signed-off-by: Luis R. Rodriguez <mcgrof@...e.com>
> ---
> include/linux/init.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/linux/init.h b/include/linux/init.h
> index 21b6d76..a0385cc 100644
> --- a/include/linux/init.h
> +++ b/include/linux/init.h
> @@ -272,7 +272,7 @@ struct obs_kernel_param {
>
> #define early_param_on_off(str_on, str_off, var, config) \
> \
> - int var = IS_ENABLED(config); \
> + int __read_mostly var = IS_ENABLED(config); \
> \
> static int __init parse_##var##_on(char *arg) \
> { \
--
Regards/Gruss,
Boris.
ECO tip #101: Trim your mails when you reply.
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