Re: [PATCH 3/4] PM/Hibernate: Use memory allocations to free memory (rev. 2)

Wu Fengguang
2009-05-03T11:51:27Z

On Sun, May 03, 2009 at 02:24:20AM +0200, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rjw-KKrjLPT3xs0@public.gmane.org>
>
> Modify the hibernation memory shrinking code so that it will make
> memory allocations to free memory instead of using an artificial
> memory shrinking mechanism for that. Remove the shrinking of
> memory from the suspend-to-RAM code, where it is not really
> necessary. Finally, remove the no longer used memory shrinking
> functions from mm/vmscan.c .
>
> [rev. 2: Use the existing memory bitmaps for marking preallocated
> image pages and use swsusp_free() from releasing them, introduce
> GFP_IMAGE, add comments describing the memory shrinking strategy.]
>
> Signed-off-by: Rafael J. Wysocki <rjw-KKrjLPT3xs0@public.gmane.org>
> ---
> kernel/power/main.c | 20 ------
> kernel/power/snapshot.c | 132 +++++++++++++++++++++++++++++++++-----------
> mm/vmscan.c | 142 ------------------------------------------------
> 3 files changed, 101 insertions(+), 193 deletions(-)
>
> Index: linux-2.6/kernel/power/snapshot.c
> ===================================================================
> --- linux-2.6.orig/kernel/power/snapshot.c
> +++ linux-2.6/kernel/power/snapshot.c
> @@ -1066,41 +1066,97 @@ void swsusp_free(void)
> buffer = NULL;
> }
>
> +/* Helper functions used for the shrinking of memory. */
> +
> +#ifdef CONFIG_HIGHMEM
> +#define GFP_IMAGE (GFP_KERNEL | __GFP_HIGHMEM | __GFP_NO_OOM_KILL)
> +#else
> +#define GFP_IMAGE (GFP_KERNEL | __GFP_NO_OOM_KILL)
> +#endif

The CONFIG_HIGHMEM test is not necessary: __GFP_HIGHMEM is always defined.

> +#define SHRINK_BITE 10000

This is ~40MB. A full scan of (for example) 8G pages will be time
consuming, not to mention we have to do it 2*(8G-500M)/40M = 384 times!

Can we make it a LONG_MAX?

Thanks,
Fengguang