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    SubjectRe: Reiser4 und LZO compression
    Nigel Cunningham wrote:
    > Hi.
    > On Tue, 2006-08-29 at 06:05 +0200, Jan Engelhardt wrote:
    >>>>>> Hmm. LZO is the best compression algorithm for the task as measured by
    >>>>>> the objectives of good compression effectiveness while still having very
    >>>>>> low CPU usage (the best of those written and GPL'd, there is a slightly
    >>>>>> better one which is proprietary and uses more CPU, LZRW if I remember
    >>>>>> right. The gzip code base uses too much CPU, though I think Edward made
    >>>>> I don't think that LZO beats LZF in both speed and compression ratio.
    >>>>> LZF is also available under GPL (dual-licensed BSD) and was choosen in favor
    >>>>> of LZO for the next generation suspend-to-disk code of the Linux kernel.
    >>>>> see:
    >>>> thanks for the info, we will compare them
    >>> For Suspend2, we ended up converting the LZF support to a cryptoapi
    >>> plugin. Is there any chance that you could use cryptoapi modules? We
    >>> could then have a hope of sharing the support.
    >> I am throwing in gzip: would it be meaningful to use that instead? The
    >> decoder (inflate.c) is already there.
    >> 06:04 shanghai:~/liblzf-1.6 > l configure*
    >> -rwxr-xr-x 1 jengelh users 154894 Mar 3 2005 configure
    >> -rwxr-xr-x 1 jengelh users 26810 Mar 3 2005 configure.bz2
    >> -rw-r--r-- 1 jengelh users 30611 Aug 28 20:32 configure.gz-z9
    >> -rw-r--r-- 1 jengelh users 30693 Aug 28 20:32 configure.gz-z6
    >> -rw-r--r-- 1 jengelh users 53077 Aug 28 20:32 configure.lzf
    > We used gzip when we first implemented compression support, and found it
    > to be far too slow. Even with the fastest compression options, we were
    > only getting a few megabytes per second. Perhaps I did something wrong
    > in configuring it, but there's not that many things to get wrong!

    All that comes to mind is the speed/quality setting -- the number from 1
    to 9. Recently, I backed up someone's hard drive using -1, and I
    believe I was still able to saturate... the _network_. Definitely try
    again if you haven't changed this, but I can't imagine I'm the first
    persson to think of it.

    From what I remember, gzip -1 wasn't faster than the disk. But at
    least for (very) repetitive data, I was wrong:

    eve:~ sanity$ time bash -c 'dd if=/dev/zero of=test bs=10m count=10; sync'
    10+0 records in
    10+0 records out
    104857600 bytes transferred in 3.261990 secs (32145287 bytes/sec)

    real 0m3.746s
    user 0m0.005s
    sys 0m0.627s
    eve:~ sanity$ time bash -c 'dd if=/dev/zero bs=10m count=10 | gzip -v1 >
    test; sync'
    10+0 records in
    10+0 records out
    104857600 bytes transferred in 2.404093 secs (43616282 bytes/sec)

    real 0m2.558s
    user 0m1.554s
    sys 0m0.680s
    eve:~ sanity$

    This was on OS X, but I think it's still valid -- this is a slightly
    older Powerbook, with a 5400 RPM drive, 1.6 ghz G4.

    -1 is still worlds better than nothing. The backup was over 15 gigs,
    down to about 6 -- loads of repetitive data, I'm sure, but that's where
    you win with compression anyway.

    Well, you use cryptoapi anyway, so it should be easy to just let the
    user pick a plugin, right?
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      Last update: 2006-08-29 10:27    [W:0.032 / U:0.492 seconds]
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