Re: Reiser4 und LZO compression

[Edward Shishkin]

Nigel Cunningham wrote:
> Hi.
>
> On Tue, 2006-08-29 at 03:23 -0500, David Masover wrote:
>
> > 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: http://www.goof.com/pcg/marc/liblzf.html
> > > > > >
> > > > > > 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)
> >  99.5%
> >
> > 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.
>
>
> Wow. That's a lot better; I guess I did get something wrong in trying to
> tune deflate. That was pre-cryptoapi though; looking at
> cryptoapi/deflate.c, I don't see any way of controlling the compression
> level. Am I missing anything?

zlib is tunable, not cryptoapi's deflate.
look at zlib_deflateInit2()

> > Well, you use cryptoapi anyway, so it should be easy to just let the 
> > user pick a plugin, right?
>
>
> Right. They can already pick deflate if they want to.
>
> Regards,
>
> Nigel

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