Re: [RFC/RFT] swsusp: image size tunable (was: Re: [PATCH][mm] swsusp: limit image size)

[Pavel Machek]

Hi!

> > > > > The tunable may be useful to people who'd like to achieve the
> > > > > maximum efficiency of suspend/resume and it would be a nice
> > > > > feature to have, I think, but let's say we'll try to implement it
> > > > > in the future, if still needed/wanted.
> > > > 
> > > > Actually the tunable turned out to be quite easy to implement and I think
> > > > I'll need it for userspace swsusp (the suspend-handling userspace
> > > > process will need to tell the kernel how much space there is for the
> > > > image).
> > > 
> > > Looks mostly okay to me, small comments below.
> 
> A cleaner version with comments etc. follows.

Looks good to me. ACK.
								Pavel

> Signed-off-by: Rafael J. Wysocki <rjw@xxxxxxx>
> 
>  Documentation/power/interface.txt |   11 +++++++++++
>  Documentation/power/swsusp.txt    |    7 ++++++-
>  kernel/power/disk.c               |   20 ++++++++++++++++++++
>  kernel/power/power.h              |    7 ++-----
>  kernel/power/swsusp.c             |   10 +++++++++-
>  5 files changed, 48 insertions(+), 7 deletions(-)
> 
> Index: linux-2.6.15-rc5-mm1/kernel/power/disk.c
> ===================================================================
> --- linux-2.6.15-rc5-mm1.orig/kernel/power/disk.c	2005-12-07 23:19:03.000000000 +0100
> +++ linux-2.6.15-rc5-mm1/kernel/power/disk.c	2005-12-10 21:10:53.000000000 +0100
> @@ -367,9 +367,29 @@
>  
>  power_attr(resume);
>  
> +static ssize_t image_size_show(struct subsystem * subsys, char *buf)
> +{
> +	return sprintf(buf, "%u\n", image_size);
> +}
> +
> +static ssize_t image_size_store(struct subsystem * subsys, const char * buf, size_t n)
> +{
> +	unsigned int size;
> +
> +	if (sscanf(buf, "%u", &size) == 1) {
> +		image_size = size;
> +		return n;
> +	}
> +
> +	return -EINVAL;
> +}
> +
> +power_attr(image_size);
> +
>  static struct attribute * g[] = {
>  	&disk_attr.attr,
>  	&resume_attr.attr,
> +	&image_size_attr.attr,
>  	NULL,
>  };
>  
> Index: linux-2.6.15-rc5-mm1/kernel/power/power.h
> ===================================================================
> --- linux-2.6.15-rc5-mm1.orig/kernel/power/power.h	2005-12-10 20:59:52.000000000 +0100
> +++ linux-2.6.15-rc5-mm1/kernel/power/power.h	2005-12-10 21:13:04.000000000 +0100
> @@ -52,11 +52,8 @@
>  extern unsigned int nr_copy_pages;
>  extern struct pbe *pagedir_nosave;
>  
> -/*
> - * Preferred image size in MB (set it to zero to get the smallest
> - * image possible)
> - */
> -#define IMAGE_SIZE	500
> +/* Preferred image size in MB (default 500) */
> +extern unsigned int image_size;
>  
>  extern asmlinkage int swsusp_arch_suspend(void);
>  extern asmlinkage int swsusp_arch_resume(void);
> Index: linux-2.6.15-rc5-mm1/kernel/power/swsusp.c
> ===================================================================
> --- linux-2.6.15-rc5-mm1.orig/kernel/power/swsusp.c	2005-12-10 20:59:52.000000000 +0100
> +++ linux-2.6.15-rc5-mm1/kernel/power/swsusp.c	2005-12-10 22:21:25.000000000 +0100
> @@ -69,6 +69,14 @@
>  
>  #include "power.h"
>  
> +/*
> + * Preferred image size in MB (tunable via /sys/power/image_size).
> + * When it is set to N, swsusp will do its best to ensure the image
> + * size will not exceed N MB, but if that is impossible, it will
> + * try to create the smallest image possible.
> + */
> +unsigned int image_size = 500;
> +
>  #ifdef CONFIG_HIGHMEM
>  unsigned int count_highmem_pages(void);
>  int save_highmem(void);
> @@ -647,7 +655,7 @@
>  			if (!tmp)
>  				return -ENOMEM;
>  			pages += tmp;
> -		} else if (size > (IMAGE_SIZE * 1024 * 1024) / PAGE_SIZE) {
> +		} else if (size > (image_size * 1024 * 1024) / PAGE_SIZE) {
>  			tmp = shrink_all_memory(SHRINK_BITE);
>  			pages += tmp;
>  		}
> Index: linux-2.6.15-rc5-mm1/Documentation/power/swsusp.txt
> ===================================================================
> --- linux-2.6.15-rc5-mm1.orig/Documentation/power/swsusp.txt	2005-10-28 02:02:08.000000000 +0200
> +++ linux-2.6.15-rc5-mm1/Documentation/power/swsusp.txt	2005-12-10 23:49:08.000000000 +0100
> @@ -27,6 +27,11 @@
>  
>  echo platform > /sys/power/disk; echo disk > /sys/power/state
>  
> +If you want to limit the suspend image size to N megabytes, do
> +
> +echo N > /sys/power/image_size
> +
> +before suspend (it is limited to 500 MB by default).
>  
>  Encrypted suspend image:
>  ------------------------
> Index: linux-2.6.15-rc5-mm1/Documentation/power/interface.txt
> ===================================================================
> --- linux-2.6.15-rc5-mm1.orig/Documentation/power/interface.txt	2005-10-28 02:02:08.000000000 +0200
> +++ linux-2.6.15-rc5-mm1/Documentation/power/interface.txt	2005-12-10 23:42:39.000000000 +0100
> @@ -41,3 +41,14 @@
>  It will only change to 'firmware' or 'platform' if the system supports
>  it. 
>  
> +/sys/power/image_size controls the size of the image created by
> +the suspend-to-disk mechanism.  It can be written a string
> +representing a non-negative integer that will be used as an upper
> +limit of the image size, in megabytes.  The suspend-to-disk mechanism will
> +do its best to ensure the image size will not exceed that number.  However,
> +if this turns out to be impossible, it will try to suspend anyway using the
> +smallest image possible.  In particular, if "0" is written to this file, the
> +suspend image will be as small as possible.
> +
> +Reading from this file will display the current image size limit, which
> +is set to 500 MB by default.

-- 
Thanks, Sharp!
-
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