linux-kernel - Re: [PATCH v1 5/8] software node: Imply kobj_to

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Date:   Sun, 28 Mar 2021 10:43:00 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Daniel Scally <djrscally@...il.com>, linux-kernel@...r.kernel.org,
        linux-media@...r.kernel.org, linux-acpi@...r.kernel.org,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Yong Zhi <yong.zhi@...el.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Bingbu Cao <bingbu.cao@...el.com>,
        Tianshu Qiu <tian.shu.qiu@...el.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>
Subject: Re: [PATCH v1 5/8] software node: Imply kobj_to_swnode() to be no-op

On Sun, Mar 28, 2021 at 12:20:09AM +0200, Andy Shevchenko wrote:
> Since we don't use structure field layout randomization
> the manual shuffling can affect some macros, in particular
> kobj_to_swnode(), which becomes a no-op when kobj member
> is the first one in the struct swnode.
> 
> Bloat-o-meter statistics:
> 
>   add/remove: 0/0 grow/shrink: 2/10 up/down: 9/-100 (-91)
>   Total: Before=7217, After=7126, chg -1.26%
> 
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> ---
>  drivers/base/swnode.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/base/swnode.c b/drivers/base/swnode.c
> index 22f81688af2c..ae53c48f84b1 100644
> --- a/drivers/base/swnode.c
> +++ b/drivers/base/swnode.c
> @@ -13,10 +13,10 @@
>  #include <linux/sysfs.h>
>  
>  struct swnode {
> -	int id;
>  	struct kobject kobj;
>  	struct fwnode_handle fwnode;
>  	const struct software_node *node;
> +	int id;

So you remove one math operation on a pointer and get a 1% size decrease
of the whole kernel?  Or just one file?

thanks,

greg k-h