On 22 July 2013 07:04, Gu Zheng <guz.fnst@xxxxxxxxxxxxxx> wrote: > On 07/22/2013 01:07 PM, Phillip Lougher wrote: > >> On 22 July 2013 04:05, Gu Zheng <guz.fnst@xxxxxxxxxxxxxx> wrote: >>> Hi Phillip, >>> Have some tests been carried out to confirm that Squashfs really >>> can get benefit from LZ4 compression, comparing with lzo? >> >> This seems to be a loaded question, in that it seems to be trying to >> reopen the "why add lz4 when we already have lzo" debate all over >> again. As LZ4 has been merged to mainline, this appears to be a >> question that has already been answered. > > No, they are different. LZ4 can be merged to mainline, because we can > see the benefit(faster compressing speed under the enabled unaligned > memory access) it brings to us comparing with lzo. The users of LZ4 that has been merged is for decompression of kernel and initramfs, not compression. So far I don't see any users of the LZ4 compression code in the kernel. So you're saying it was merged for fast compression despite there being no users of it? > But it's hard to say that it also really can bring benefit to Squashfs. Prejudiced statement without any evidence, if that's your contention prove it. > >> >> As far as Squashfs is concerned, I believe it is important to give >> people the choice of using LZ4 to compress Squashfs filesystems now >> its been mainlined. As far as expected benefits are concerned, >> Squashfs' use in embedded systems is very similar to compressing >> kernels and initramfs data, in that it tends to be used to compress >> root filesystems. As such the benefits of using LZ4 in Squashfs >> should be broadly similar to using LZ4 to compress kernels and >> initramfs data. Ultimately it is up to people to experiment and >> choose whatever compression is best for their systems. > > Yes, but the premise is that using LZ4 in Squashfs is better than lzo > in at least one actual situation. > No. All it takes is for LZ4 to be better/faster at decompressing the kernel or initramfs to make it advantageous to use LZ4 for Squashfs, thus avoiding the overhead of another decompressor in the kernel.. >> >> People are welcome to try the patches out and report their findings. > > Let's look and see other guys' feedbacks, they are more persuasive.:) Suit yourself, maybe when you start using evidence rather than unsubstantiated assertions, you'll be more persuasive too. So far all I see is wind. Phillip > > Regards, > Gu > >> >> Phillip >> >>> >>> Thanks, >>> Gu >>> >>> On 07/22/2013 10:21 AM, Phillip Lougher wrote: >>> >>>> Hi >>>> >>>> Now that LZ4 compression support is in 3.11-rc1, I have written the >>>> following two patches for Squashfs to use it. >>>> >>>> Phillip Lougher (2): >>>> Squashfs: add LZ4 compression support >>>> Squashfs: Add LZ4 compression configuration option >>>> >>>> Documentation/filesystems/squashfs.txt | 8 +- >>>> fs/squashfs/Kconfig | 15 +++ >>>> fs/squashfs/Makefile | 1 + >>>> fs/squashfs/decompressor.c | 7 ++ >>>> fs/squashfs/decompressor.h | 4 + >>>> fs/squashfs/lz4_wrapper.c | 163 ++++++++++++++++++++++++++++++++ >>>> fs/squashfs/squashfs_fs.h | 1 + >>>> 7 files changed, 195 insertions(+), 4 deletions(-) >>>> create mode 100644 fs/squashfs/lz4_wrapper.c >>>> >>>> These patches are also available in the git tree here: >>>> >>>> browse: https://git.kernel.org/cgit/linux/kernel/git/pkl/squashfs-lz4.git >>>> git clone: git://git.kernel.org/pub/scm/linux/kernel/git/pkl/squashfs-lz4.git >>>> >>>> LZ4 support has (obviously) also been added to the squashfs-tools >>>> (Mksquashfs and Unsquashfs). This is available from the Squashfs-tools >>>> git repository here: >>>> >>>> browse: https://git.kernel.org/cgit/fs/squashfs/squashfs-tools.git >>>> git clone: git://git.kernel.org/pub/scm/fs/squashfs/squashfs-tools.git >>>> >>>> When building the squashfs-tools edit the Makefile to enable LZ4 >>>> support (by default it is disabled). >>>> >>>> LZ4 compression can be specified by using the -comp option, e.g. >>>> % mksquashfs xxx img.sqsh -comp lz4 >>>> >>>> The use of LZ4 high compression can be specified using -Xhc, e.g. >>>> >>>> % mksquashfs xxx img.sqsh -comp lz4 -Xhc >>>> >>>> Phillip >>>> -- >>>> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in >>>> the body of a message to majordomo@xxxxxxxxxxxxxxx >>>> More majordomo info at http://vger.kernel.org/majordomo-info.html >>>> Please read the FAQ at http://www.tux.org/lkml/ >>>> >>> >>> >> > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- To unsubscribe from this list: send the line "unsubscribe linux-embedded" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
