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.p...@linux.intel.com>
---
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.
+
config KERNEL_GZIP
bool "Gzip"
depends on HAVE_KERNEL_GZIP
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index 2edbcad..384128d 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -344,6 +344,14 @@ cmd_lz4 = (cat $(filter-out FORCE,$^) | \
lz4c -l -c1 stdin stdout && $(call size_append, $(filter-out
FORCE,$^))) > $@ || \
(rm -f $@ ; false)
+# RAW
+# ---------------------------------------------------------------------------
+quiet_cmd_raw = RAW $@
+cmd_raw = (cat $(filter-out FORCE,$^) && \
+ $(call size_append, $(filter-out FORCE,$^))) > $@ || \
+ (rm -f $@ ; false)
+
+
# U-Boot mkimage
# ---------------------------------------------------------------------------
--
1.8.3.1
