[PATCH] x86/boot: Support uncompressed kernel

* [PATCH] x86/boot: Support uncompressed kernel
@ 2017-03-23 12:51 Chao Peng
  2017-03-23 15:07 ` Yinghai Lu
  2017-03-24  8:09 ` Michal Marek
  0 siblings, 2 replies; 12+ messages in thread
From: Chao Peng @ 2017-03-23 12:51 UTC (permalink / raw)
  To: H. Peter Anvin, Thomas Gleixner, Ingo Molnar
  Cc: x86, Michal Marek, Kees Cook, Yinghai Lu, Baoquan He, H.J. Lu,
	Paul Bolle, Masahiro Yamada, Chao Peng, Borislav Petkov,
	Andrew Morton, Arnd Bergmann, Petr Mladek, David S. Miller,
	Paul E. McKenney, Andy Lutomirski, Thomas Garnier, Nicolas Pitre,
	Tejun Heo, Daniel Mack, Sebastian Andrzej Siewior,
	Sergey Senozhatsky, Helge Deller, Rik van Riel, linux-kernel,
	linux-kbuild

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@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

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