Re: [PATCH RFC 1/3] Decompressors: Add XZ decompressor module
On 2010-11-25 Andrew Morton wrote: On Wed, 24 Nov 2010 22:51:52 +0200 Lasse Collin lasse.col...@tukaani.org wrote: This patch: Add the main decompression code (xz_dec), testing module (xz_dec_test), wrapper script (xz_wrap.sh) for the xz command line tool, and documentation. The xz_dec module is enough to have a usable XZ decompressor e.g. for Squashfs. I'm not seeing any documentation which tells me how to create, install and execute xs-compressed kernels. There are new makefile targets? The last paragraph under XZ related components in the kernel in Documentation/xz.txt mentions xzkern and xzmisc commands available for makefiles. They are defined in scripts/Makefile.lib and have some comments as documentation there too. The Kconfig options to enable XZ-compressed kernel are added in the second patch. There is already an option to select the kernel compression method so I only added XZ to that list. I assume that people will find this option just like they have been able to find the other compression methods. +#define bcj_x86_test_msbyte(b) ((b) == 0x00 || (b) == 0xFF) This should be written in C. It looks nicer, and so bcj_x86_test_msbyte(*p++) won't explode. Thanks. It's fixed in XZ Embedded git repository now: git clone http://git.tukaani.org/xz-embedded.git (clone only, no WWW for now) I will post updated patches when needed. +static noinline_for_stack size_t bcj_x86( hm, but it uses little stack space. I wrote that code 19 months ago and now it looks odd to me too. I remember that my idea was to minimize stack usage in this call stack: xz_dec_run() - xz_dec_bcj_run() - xz_dec_lzma2_run() - ... I wanted to prevent the BCJ filters from being inlined into xz_dec_bcj_run() because inlining would have increased the maximum stack usage by 100-150 bytes. The BCJ filters are called via bcj_apply() which is called in two places from xz_dec_bcj_run(). Since there are two calls to bcj_apply(), GCC won't inline it. It will only inline the BCJ filters into bcj_apply() and that's OK. So noinline_for_stack does nothing good here. Maybe my early version had only one call to bcj_apply() or something like that. Anyway, I removed noinline_for_stacks. I tested it also when only one BCJ filter is enabled and with a few different GCC versions. +static noinline_for_stack size_t bcj_x86( + struct xz_dec_bcj *s, uint8_t *buf, size_t size) The preferred style is static noinline_for_stack size_t bcj_x86(struct xz_dec_bcj *s, uint8_t *buf, size_t size) or static noinline_for_stack size_t bcj_x86(struct xz_dec_bcj *s, uint8_t *buf, size_t size) (lots of dittoes) Fixed. -- Lasse Collin | IRC: Larhzu @ IRCnet Freenode -- To unsubscribe from this list: send the line unsubscribe linux-embedded in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH RFC 1/3] Decompressors: Add XZ decompressor module
On Wed, 24 Nov 2010 22:51:52 +0200 Lasse Collin lasse.col...@tukaani.org wrote: From: Lasse Collin lasse.col...@tukaani.org In userspace, the .lzma format has become mostly a legacy file format that got superseded by the .xz format. Similarly, LZMA Utils was superseded by XZ Utils. These patches add support for XZ decompression into the kernel. Most of the code is as is from XZ Embedded http://tukaani.org/xz/embedded.html. It was written for the Linux kernel but is usable in other projects too. Advantages of XZ over the current LZMA code in the kernel: - Nice API that can be used by other kernel modules; it's not limited to kernel, initramfs, and initrd decompression. - Integrity check support (CRC32) - BCJ filters improve compression of executable code on certain architectures. These together with LZMA2 can produce a few percent smaller kernel or Squashfs images than plain LZMA without making the decompression slower. This patch: Add the main decompression code (xz_dec), testing module (xz_dec_test), wrapper script (xz_wrap.sh) for the xz command line tool, and documentation. The xz_dec module is enough to have a usable XZ decompressor e.g. for Squashfs. I'm not seeing any documentation which tells me how to create, install and execute xs-compressed kernels. There are new makefile targets? ... +#define bcj_x86_test_msbyte(b) ((b) == 0x00 || (b) == 0xFF) This should be written in C. It looks nicer, and so bcj_x86_test_msbyte(*p++) won't explode. +static noinline_for_stack size_t bcj_x86( hm, but it uses little stack space. +static noinline_for_stack size_t bcj_x86( + struct xz_dec_bcj *s, uint8_t *buf, size_t size) The preferred style is static noinline_for_stack size_t bcj_x86(struct xz_dec_bcj *s, uint8_t *buf, size_t size) or static noinline_for_stack size_t bcj_x86(struct xz_dec_bcj *s, uint8_t *buf, size_t size) (lots of dittoes) -- To unsubscribe from this list: send the line unsubscribe linux-embedded in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH RFC 1/3] Decompressors: Add XZ decompressor module
On 11/24/2010 02:50 PM, H. Peter Anvin wrote: Logically it should be an additional CONFIG option like we currently have for the other compression formats. And so it is (it's in the latter patches). -hpa -- To unsubscribe from this list: send the line unsubscribe linux-embedded in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
