Re: [PATCH]: Compress hibernation image with LZO (in-kernel)

[Nigel Cunningham]

Hi.

On 04/08/10 14:04, Bojan Smojver wrote:
> On Wed, 2010-08-04 at 12:47 +1000, Bojan Smojver wrote:
> > Points taken for all the other comments. Thank you.
>
> Style wise, does this look better?
>
> PS. Don't worry about contents yet - still working out the kinks.

Okay.

> diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig
> index ca6066a..cb57eb9 100644
> --- a/kernel/power/Kconfig
> +++ b/kernel/power/Kconfig
> @@ -137,6 +137,8 @@ config SUSPEND_FREEZER
>   config HIBERNATION
>   	bool "Hibernation (aka 'suspend to disk')"
>   	depends on PM&&  SWAP&&  ARCH_HIBERNATION_POSSIBLE
> +	select LZO_COMPRESS
> +	select LZO_DECOMPRESS

But, having said 'okay' above, I should point out that you might want to 
select CRYPTO too, since LZO depends on it. (And perhaps I should ask 
whether you should be using cryptoapi rather than LZO directly?)

>   	select SUSPEND_NVS if HAS_IOMEM
>   	---help---
>   	  Enable the suspend to disk (STD) functionality, which is usually
> diff --git a/kernel/power/swap.c b/kernel/power/swap.c
> index b0bb217..1515e2c 100644
> --- a/kernel/power/swap.c
> +++ b/kernel/power/swap.c
> @@ -24,6 +24,7 @@
>   #include<linux/swapops.h>
>   #include<linux/pm.h>
>   #include<linux/slab.h>
> +#include<linux/lzo.h>
>
>   #include "power.h"
>
> @@ -357,6 +358,30 @@ static int swap_writer_finish(struct swap_map_handle *handle,
>   	return error;
>   }
>
> +/* We need to remember how much compressed data we need to read. */
> +#define LZO_HEADER	sizeof(size_t)
> +
> +/* Number of pages/bytes we'll compress at a time. */
> +#define LZO_UNC_PAGES	64
> +#define LZO_UNC_SIZE	(LZO_UNC_PAGES * PAGE_SIZE)
> +
> +/* Number of pages/bytes we need for compressed data (worst case). */
> +#define LZO_CMP_PAGES	DIV_ROUND_UP(lzo1x_worst_compress(LZO_UNC_SIZE) + \
> +			             LZO_HEADER, PAGE_SIZE)
> +#define LZO_CMP_SIZE	(LZO_CMP_PAGES * PAGE_SIZE)
> +
> +/* As per examples/overlap.c in lzo distribution, we need to add more space
> + * to the end of the buffer in order to perform overlapping compression. We
> + * also add LZO_HEADER, because our compressed data starts at that offset.
> + * Then we round it off on PAGE_SIZE boundary, so that we can copy full pages
> + * safely. We call this overhead. Magic numbers and formula below.
> + */

Yeah, that's much better; thanks.

Nigel
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