[OpenWrt-Devel] [PATCH] build: allow alternative gzip image compression utility

[Ian Cooper]

Allow the user to specify an alternative option-compatible gzip
utility such as the parallel pigz gzip utility, which speeds up
compression of target images and archives considerably.

Signed-off-by: Ian Cooper <iancooper at hotmail.com>
---
On my 4-core i7-4790s, it takes a full 10 minutes to build the images
for my x86_64 build as there are lots of packages included in the image.

The largest part of this time is the gzip compression. The pigz utility
is much faster, even on my limited 4 cores. Below is the timing of a
make target/install for the gzip and pigz utilities

using gzip on 4-core i7-4790

real    9m48.480s
user    8m41.578s
sys     0m44.228s

using pigz on 4-core i7-4790

real    3m34.367s
user    11m23.081s
sys     0m49.984s

 config/Config-images.in   | 10 ++++++++++
 include/image-commands.mk |  2 +-
 include/image.mk          | 10 ++++++----
 3 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/config/Config-images.in b/config/Config-images.in
index 4c54ac9399..7c3bc2760e 100644
--- a/config/Config-images.in
+++ b/config/Config-images.in
@@ -287,4 +287,14 @@ menu "Target Images"
 		  it will be mounted by PARTUUID which makes the kernel find the
 		  appropriate disk automatically.
 
+	config TARGET_IMAGE_COMPRESSION_UTILITY
+		string
+		prompt "Gzip image compression utility"
+		default "gzip"
+		help
+		  Specify the name of the image compression binary used to gzip
+		  compress images. This utility must be option compatible with
+		  gzip. A good alternative would be the parallel gzip utility
+		  pigz.
+
 endmenu
diff --git a/include/image-commands.mk b/include/image-commands.mk
index e7db7128b4..faba8658c0 100644
--- a/include/image-commands.mk
+++ b/include/image-commands.mk
@@ -174,7 +174,7 @@ define Build/lzma-no-dict
 endef
 
 define Build/gzip
-	gzip -f -9n -c $@ $(1) > $@.new
+	$(call qstrip,$(CONFIG_TARGET_IMAGE_COMPRESSION_UTILITY)) -f -9n -c $@ $(1) > $@.new
 	@mv $@.new $@
 endef
 
diff --git a/include/image.mk b/include/image.mk
index 984b64fb9c..61182a22ac 100644
--- a/include/image.mk
+++ b/include/image.mk
@@ -151,7 +151,7 @@ endef
 ifdef CONFIG_TARGET_IMAGES_GZIP
   define Image/Gzip
 	rm -f $(1).gz
-	gzip -9n $(1)
+	$(call qstrip,$(CONFIG_TARGET_IMAGE_COMPRESSION_UTILITY)) -9n $(1)
   endef
 endif
 
@@ -317,13 +317,15 @@ ifdef CONFIG_TARGET_ROOTFS_TARGZ
   define Image/Build/targz
 	$(TAR) -cp --numeric-owner --owner=0 --group=0 --mode=a-s --sort=name \
 		$(if $(SOURCE_DATE_EPOCH),--mtime="@$(SOURCE_DATE_EPOCH)") \
-		-C $(TARGET_DIR)/ . | gzip -9n > $(BIN_DIR)/$(IMG_PREFIX)$(if $(PROFILE_SANITIZED),-$(PROFILE_SANITIZED))-rootfs.tar.gz
+		-C $(TARGET_DIR)/ . | $(call qstrip,$(CONFIG_TARGET_IMAGE_COMPRESSION_UTILITY)) \
+		-9n > $(BIN_DIR)/$(IMG_PREFIX)$(if $(PROFILE_SANITIZED),-$(PROFILE_SANITIZED))-rootfs.tar.gz
   endef
 endif
 
 ifdef CONFIG_TARGET_ROOTFS_CPIOGZ
   define Image/Build/cpiogz
-	( cd $(TARGET_DIR); find . | cpio -o -H newc -R root:root | gzip -9n >$(BIN_DIR)/$(IMG_ROOTFS).cpio.gz )
+	( cd $(TARGET_DIR); find . | cpio -o -H newc -R root:root | \
+	$(call qstrip,$(CONFIG_TARGET_IMAGE_COMPRESSION_UTILITY)) -9n >$(BIN_DIR)/$(IMG_ROOTFS).cpio.gz )
   endef
 endif
 
@@ -567,7 +569,7 @@ define Device/Build/image
   .IGNORE: $(BIN_DIR)/$(call IMAGE_NAME,$(1),$(2))
 
   $(BIN_DIR)/$(call IMAGE_NAME,$(1),$(2)).gz: $(KDIR)/tmp/$(call IMAGE_NAME,$(1),$(2))
-	gzip -c -9n $$^ > $$@
+	$(call qstrip,$(CONFIG_TARGET_IMAGE_COMPRESSION_UTILITY)) -c -9n $$^ > $$@
 
   $(BIN_DIR)/$(call IMAGE_NAME,$(1),$(2)): $(KDIR)/tmp/$(call IMAGE_NAME,$(1),$(2))
 	cp $$^ $$@
-- 
2.25.1


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