[PATCH] ARM: add support for uncompressed uImage kernel

[PATCH] ARM: add support for uncompressed uImage kernel

[Alexander Stein]

Signed-off-by: Alexander Stein <alexander.stein@systec-electronic.com>
---
 arch/arm/boot/Makefile |   10 ++++++++--
 init/Kconfig           |    7 +++++++
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/arch/arm/boot/Makefile b/arch/arm/boot/Makefile
index 4a590f4..37618b8 100644
--- a/arch/arm/boot/Makefile
+++ b/arch/arm/boot/Makefile
@@ -77,11 +77,17 @@ else
 $(obj)/uImage: STARTADDR=$(LOADADDR)
 endif
 
-$(obj)/uImage:	$(obj)/zImage FORCE
+ifeq ($(CONFIG_KERNEL_NONE),y)
+ARM_IMAGE := Image
+else
+ARM_IMAGE := zImage
+endif
+
+$(obj)/uImage:	$(obj)/$(ARM_IMAGE) FORCE
 	$(call if_changed,uimage)
 	@echo '  Image $@ is ready'
 
-$(obj)/bootp/bootp: $(obj)/zImage initrd FORCE
+$(obj)/bootp/bootp: $(obj)/$(ARM_IMAGE) initrd FORCE
 	$(Q)$(MAKE) $(build)=$(obj)/bootp $@
 	@:
 
diff --git a/init/Kconfig b/init/Kconfig
index 88c1046..355d7a5 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -155,6 +155,13 @@ choice
 
 	  If in doubt, select 'gzip'
 
+config KERNEL_NONE
+	bool "None"
+	depends on ARM
+	help
+	  If you want to use get a fast startup at the cost of kernel size
+	  you can use an uncompressed kernel.
+
 config KERNEL_GZIP
 	bool "Gzip"
 	depends on HAVE_KERNEL_GZIP
-- 
1.7.2.2

[PATCH] ARM: add support for uncompressed uImage kernel

[Russell King - ARM Linux]

Is it really faster to copy an uncompressed image than it is to
decompress using LZMA with caches on?

Remember that in terms of fast boot, uboot sucks - it's way over the
top of what you need.  Eg, it always copies the image to RAM before
executing it.  That gives two problems:

1. the image has to be copied, which takes time
2. the image then decompresses itself, but because its more often than
   not living at the address which the decompressed image has to reside,
   it then has to copy the decompressed image afterwards.

(2) is solved by loading the kernel compressed image elsewhere in memory.
(1) is solved by having a boot loader which can call the image where-ever
it resides (eg, in flash) and using the ZBOOT_ROM options.

I suspect that if you do both 1 and 2, you'll be faster than having uboot
copy an uncompressed image into system memory.

On Tue, Nov 09, 2010 at 02:50:56PM +0100, Alexander Stein wrote:
> Signed-off-by: Alexander Stein <alexander.stein@systec-electronic.com>
> ---
>  arch/arm/boot/Makefile |   10 ++++++++--
>  init/Kconfig           |    7 +++++++
>  2 files changed, 15 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm/boot/Makefile b/arch/arm/boot/Makefile
> index 4a590f4..37618b8 100644
> --- a/arch/arm/boot/Makefile
> +++ b/arch/arm/boot/Makefile
> @@ -77,11 +77,17 @@ else
>  $(obj)/uImage: STARTADDR=$(LOADADDR)
>  endif
>  
> -$(obj)/uImage:	$(obj)/zImage FORCE
> +ifeq ($(CONFIG_KERNEL_NONE),y)
> +ARM_IMAGE := Image
> +else
> +ARM_IMAGE := zImage
> +endif
> +
> +$(obj)/uImage:	$(obj)/$(ARM_IMAGE) FORCE
>  	$(call if_changed,uimage)
>  	@echo '  Image $@ is ready'
>  
> -$(obj)/bootp/bootp: $(obj)/zImage initrd FORCE
> +$(obj)/bootp/bootp: $(obj)/$(ARM_IMAGE) initrd FORCE
>  	$(Q)$(MAKE) $(build)=$(obj)/bootp $@
>  	@:
>  
> diff --git a/init/Kconfig b/init/Kconfig
> index 88c1046..355d7a5 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -155,6 +155,13 @@ choice
>  
>  	  If in doubt, select 'gzip'
>  
> +config KERNEL_NONE
> +	bool "None"
> +	depends on ARM
> +	help
> +	  If you want to use get a fast startup at the cost of kernel size
> +	  you can use an uncompressed kernel.
> +
>  config KERNEL_GZIP
>  	bool "Gzip"
>  	depends on HAVE_KERNEL_GZIP
> -- 
> 1.7.2.2
> 
> 
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel at lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

[PATCH] ARM: add support for uncompressed uImage kernel

[Uwe Kleine-König]

On Tue, Nov 09, 2010 at 02:04:55PM +0000, Russell King - ARM Linux wrote:
> Is it really faster to copy an uncompressed image than it is to
> decompress using LZMA with caches on?
> 
> Remember that in terms of fast boot, uboot sucks - it's way over the
> top of what you need.  Eg, it always copies the image to RAM before
> executing it.  That gives two problems:
Last time I checked (which is a few years ago) U-Boot was well able to
start a ZBOOT_ROM image.  I'd be surprised if U-Boot lost that ability.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-K?nig            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |

[PATCH] ARM: add support for uncompressed uImage kernel

[Sascha Hauer]

On Tue, Nov 09, 2010 at 02:04:55PM +0000, Russell King - ARM Linux wrote:
> Is it really faster to copy an uncompressed image than it is to
> decompress using LZMA with caches on?
> 

At least on an i.MX35 I can read a bigger image from NAND faster than I
can read + uncompress a smaller image. ZBOOT_ROM is no option for NAND.
Reading from NAND is done with mmu/dcache on in this case.

Sascha

-- 
Pengutronix e.K.                           |                             |
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[PATCH] ARM: add support for uncompressed uImage kernel

[Albin Tonnerre]

On Tue, Nov 9, 2010 at 3:04 PM, Russell King - ARM Linux
<linux@arm.linux.org.uk> wrote:
> Is it really faster to copy an uncompressed image than it is to
> decompress using LZMA with caches on?

In my experience, using LZMA is painfully slow on older ARM CPUs.

If you really need to boot quickly you might want to try LZO, which
should give you results close to the uncompressed performance. It
might still be slower though, especially if you're able to load your
kernel image to memory fairly quickly

Regards,
-- 
Albin Tonnerre

[PATCH] ARM: add support for uncompressed uImage kernel

[Alexander Stein]

Soory for late answer,

On Saturday 13 November 2010, 11:47:41 Albin Tonnerre wrote:
> <linux@arm.linux.org.uk> wrote:
> > Is it really faster to copy an uncompressed image than it is to
> > decompress using LZMA with caches on?
> 
> In my experience, using LZMA is painfully slow on older ARM CPUs.
> 
> If you really need to boot quickly you might want to try LZO, which
> should give you results close to the uncompressed performance. It
> might still be slower though, especially if you're able to load your
> kernel image to memory fairly quickly

We only have experience with GZIP. Our compressed kernel is ~1,8MB and 
uncompressed ~4MB.
On an AT91 ARM9 SoC the decompression takes about 1-2s of time. Caches should 
be disabled, as far as I could see in decompression code.
Copying the uncompressed kernel from NOR to SD-RAM takes about 140ms. So if 
you can afford the additional storage need, simply copying the uncompressed 
kernel is much faster than copying the compressed kernel which decompresses 
itself.

Best regards,
Alexander

[PATCH] ARM: add support for uncompressed uImage kernel

[Uwe Kleine-König]

On Thu, Nov 18, 2010 at 08:38:26AM +0100, Alexander Stein wrote:
> Soory for late answer,
> 
> On Saturday 13 November 2010, 11:47:41 Albin Tonnerre wrote:
> > <linux@arm.linux.org.uk> wrote:
> > > Is it really faster to copy an uncompressed image than it is to
> > > decompress using LZMA with caches on?
> > 
> > In my experience, using LZMA is painfully slow on older ARM CPUs.
> > 
> > If you really need to boot quickly you might want to try LZO, which
> > should give you results close to the uncompressed performance. It
> > might still be slower though, especially if you're able to load your
> > kernel image to memory fairly quickly
> 
> We only have experience with GZIP. Our compressed kernel is ~1,8MB and 
> uncompressed ~4MB.
> On an AT91 ARM9 SoC the decompression takes about 1-2s of time. Caches should 
> be disabled, as far as I could see in decompression code.
Caches are enabled in line 248 of
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=blob;f=arch/arm/boot/compressed/head.S;h=6825c34646d4e02f24b0eefe7ab4e012bca05208;hb=HEAD

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-K?nig            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |

[PATCH] ARM: add support for uncompressed uImage kernel

[Russell King - ARM Linux]

On Thu, Nov 18, 2010 at 08:38:26AM +0100, Alexander Stein wrote:
> We only have experience with GZIP. Our compressed kernel is ~1,8MB and 
> uncompressed ~4MB.
> On an AT91 ARM9 SoC the decompression takes about 1-2s of time. Caches should 
> be disabled, as far as I could see in decompression code.

Are you sure?  ARM9 is supposed to be ARMv4T, which is covered by this
entry in the proc_types table:

                .word   0x00020000              @ ARMv4T
                .word   0x000f0000
                W(b)    __armv4_mmu_cache_on
                W(b)    __armv4_mmu_cache_off
                W(b)    __armv4_mmu_cache_flush

So caches _should_ be enabled.

[PATCH] ARM: add support for uncompressed uImage kernel

[Alexander Stein]

Hello,

On Thursday 18 November 2010, 10:10:46 Russell King - ARM Linux wrote:
> On Thu, Nov 18, 2010 at 08:38:26AM +0100, Alexander Stein wrote:
> > We only have experience with GZIP. Our compressed kernel is ~1,8MB and
> > uncompressed ~4MB.
> > On an AT91 ARM9 SoC the decompression takes about 1-2s of time. Caches
> > should be disabled, as far as I could see in decompression code.
> 
> Are you sure?  ARM9 is supposed to be ARMv4T, which is covered by this
> entry in the proc_types table:
> 
>                 .word   0x00020000              @ ARMv4T
>                 .word   0x000f0000
>                 W(b)    __armv4_mmu_cache_on
>                 W(b)    __armv4_mmu_cache_off
>                 W(b)    __armv4_mmu_cache_flush
> 
> So caches _should_ be enabled.

I'm _not_ sure. That was a long time ago and I only did a short look into the 
decompression/setup code.
After I noticed using the uncompressed kernel is much faster, I didn't 
investigate further.

Best regards,
Alexander

[PATCH] ARM: add support for uncompressed uImage kernel

[Uwe Kleine-König]

On Tue, Nov 09, 2010 at 02:50:56PM +0100, Alexander Stein wrote:
> Signed-off-by: Alexander Stein <alexander.stein@systec-electronic.com>
Quite some time ago I suggested something similar.  I'm sure you can
find the mail in the archives.  The result of my patch was the
introduction of a few more Make-targets:

	uImage -> uimage(Image)
	uzImage -> uimage(zImage) (== today's uImage)
	uImagegz -> uimage(gzip(Image))

Russell objected that though.
Today I don't use the kernel Makefile anymore to build uImages, but let
ptxdist do that for me.

Best regards
Uwe
-- 
Pengutronix e.K.                           | Uwe Kleine-K?nig            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |