On 2017-03-23 13:51, Chao Peng wrote:
> Compressed kernel has its own drawback: uncompressing takes time. Even
> though the time is short enough to ignore for most cases but for cases that
> time is critical this is still a big number. In our on-going optimization
> for kernel boot time, the measured overall kernel boot time is ~90ms while
> the uncompressing takes ~50ms with gzip.
>
> The patch adds a 'CONFIG_KERNEL_RAW' configure choice so the built binary
> can have no uncompressing at all. The experiment shows:
>
> kernel kernel size time in decompress_kernel
> compressed (gzip) 3.3M 53ms
> uncompressed 14M 3ms
>
> Signed-off-by: Chao Peng <chao.p.peng@xxxxxxxxxxxxxxx>
> ---
> arch/x86/boot/compressed/Makefile | 3 +++
> arch/x86/boot/compressed/misc.c | 14 ++++++++++++++
> init/Kconfig | 7 +++++++
> scripts/Makefile.lib | 8 ++++++++
> 4 files changed, 32 insertions(+)
>
> diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
> index f9ce75d..fc0e1c0 100644
> --- a/arch/x86/boot/compressed/Makefile
> +++ b/arch/x86/boot/compressed/Makefile
> @@ -73,6 +73,8 @@ $(obj)/vmlinux.relocs: vmlinux FORCE
> vmlinux.bin.all-y := $(obj)/vmlinux.bin
> vmlinux.bin.all-$(CONFIG_X86_NEED_RELOCS) += $(obj)/vmlinux.relocs
>
> +$(obj)/vmlinux.bin.raw: $(vmlinux.bin.all-y) FORCE
> + $(call if_changed,raw)
> $(obj)/vmlinux.bin.gz: $(vmlinux.bin.all-y) FORCE
> $(call if_changed,gzip)
> $(obj)/vmlinux.bin.bz2: $(vmlinux.bin.all-y) FORCE
> @@ -86,6 +88,7 @@ $(obj)/vmlinux.bin.lzo: $(vmlinux.bin.all-y) FORCE
> $(obj)/vmlinux.bin.lz4: $(vmlinux.bin.all-y) FORCE
> $(call if_changed,lz4)
>
> +suffix-$(CONFIG_KERNEL_RAW) := raw
> suffix-$(CONFIG_KERNEL_GZIP) := gz
> suffix-$(CONFIG_KERNEL_BZIP2) := bz2
> suffix-$(CONFIG_KERNEL_LZMA) := lzma
> diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
> index 79dac17..fb3cd43 100644
> --- a/arch/x86/boot/compressed/misc.c
> +++ b/arch/x86/boot/compressed/misc.c
> @@ -123,6 +123,20 @@ static char *vidmem;
> static int vidport;
> static int lines, cols;
>
> +#ifdef CONFIG_KERNEL_RAW
> +#include <linux/decompress/mm.h>
> +static int __decompress(unsigned char *buf, long len,
> + long (*fill)(void*, unsigned long),
> + long (*flush)(void*, unsigned long),
> + unsigned char *outbuf, long olen,
> + long *pos,
> + void (*error)(char *x))
> +{
> + memcpy(outbuf, buf, olen);
> + return 0;
> +}
> +#endif
> +
> #ifdef CONFIG_KERNEL_GZIP
> #include "../../../../lib/decompress_inflate.c"
> #endif
> diff --git a/init/Kconfig b/init/Kconfig
> index 2232080..1db2ea2 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -137,6 +137,13 @@ choice
>
> If in doubt, select 'gzip'
>
> +config KERNEL_RAW
> + bool "RAW"
> + help
> + No compression. It creates much bigger kernel and uses much more
> + space (disk/memory) than other choices. It can be useful when
> + decompression speed is the most concern while space is not a problem.
This needs to depend on a HAVE_KERNEL_RAW config that is selected by the
architectures that implement this target (x86).
Michal
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