Date: Wed, 3 Oct 2012 11:37:39 -0600 From: John Nielsen <lists@jnielsen.net> To: Yamagi Burmeister <lists@yamagi.org> Cc: bfalk_bsd@brandonfa.lk, freebsd-hackers@freebsd.org Subject: Re: SMP Version of tar Message-ID: <E1A4E8ED-189F-48F1-BC36-6960E33EB5E4@jnielsen.net> In-Reply-To: <20121002083634.3103fe958508a4026384ac96@yamagi.org> References: <5069C9FC.6020400@brandonfa.lk> <87549776-9051-4B4B-8D53-DAE6D51C2A94@kientzle.com> <20121002083634.3103fe958508a4026384ac96@yamagi.org>
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On Oct 2, 2012, at 12:36 AM, Yamagi Burmeister <lists@yamagi.org> wrote: > On Mon, 1 Oct 2012 22:16:53 -0700 > Tim Kientzle <tim@kientzle.com> wrote: > >> There are a few different parallel command-line compressors and decompressors in ports; experiment a lot (with large files being read from and/or written to disk) and see what the real effect is. In particular, some decompression algorithms are actually faster than memcpy() when run on a single processor. Parallelizing such algorithms is not likely to help much in the real world. >> >> The two popular algorithms I would expect to benefit most are bzip2 compression and lzma compression (targeting xz or lzip format). For decompression, bzip2 is block-oriented so fits SMP pretty naturally. Other popular algorithms are stream-oriented and less amenable to parallelization. >> >> Take a careful look at pbzip2, which is a parallelized bzip2/bunzip2 implementation that's already under a BSD license. You should be able to get a lot of ideas about how to implement a parallel compression algorithm. Better yet, you might be able to reuse a lot of the existing pbzip2 code. >> >> Mark Adler's pigz is also worth studying. It's also license-friendly, and is built on top of regular zlib, which is a nice technique when it's feasible. > > Just a small note: There's a parallel implementation of xz called > "pixz". It's build atop of liblzma and libarchiv and stands under a > BSD style license. See: https://github.com/vasi/pixz Maybe it's > possible to reuse most of the code. See also below, which has some bugfixes/improvements that AFAIK were never committed in the original project (though they were submitted). https://github.com/jlrobins/pixz JNhelp
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