Messages in this thread | | | From | Rob Landley <> | Subject | Re: [PATCH] create option to compress initramfs within the kernel | Date | Sat, 22 Nov 2008 19:32:11 -0600 |
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On Saturday 22 November 2008 11:30:13 frans wrote: > Below is a patch to make compression of the initramfs image optional. > Sumbitted to LKML as there is no MAINTAINER listed for initramfs. > > Rationale is that if you create a compressed kernel image (e.g. by > make bzImage) it is not very efficient and useful to compress initramfs > as the initramfs will be compressed anyway when the kernel image is > compressed.
Actually it saves intermediate space (the cpio archive and the decompressed ramfs coexist during the decompression, until the kernel can free the cpio archive), so it does serve a purpose. (Given cache effects leaving it compressed may actually wind up being faster on modern CPUs because it dirties fewer pages.)
It also eats CPU, which is at more of a premium than memory on some little battery powered wind-up boxes. But I'd be happier seeing some actual benchmark numbers on a device that would actually _notice_ this change.
> @@ -257,6 +258,9 @@ while [ $# -gt 0 ]; do > default_list="$arg" > ${dep_list}default_initramfs > ;; > + "-c") # compress > + compress=1 > + ;;
You're changing the default behavior for people who run this script directly. Just FYI.
> --- a/usr/Kconfig > +++ b/usr/Kconfig > @@ -44,3 +44,14 @@ config INITRAMFS_ROOT_GID > owned by group root in the initial ramdisk image. > > If you are not sure, leave it set to "0". > + > +config INITRAMFS_COMPRESS > + bool "Compress initramfs image" > + default y > + help > + If you want a compressed initramfs image in your kernel say y > + If you do not want your initramfs image to be compressed say n. > + A compressed initramfs is generally not useful if you also have a > + compressed kernel (vmlinuz, bzImage).
This should probably be in the CONFIG_EMBEDDED menu.
Rob
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