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Date:      Sun, 7 Oct 2012 10:52:27 -0700
From:      Tim Kientzle <tim@kientzle.com>
To:        Wojciech Puchar <wojtek@wojtek.tensor.gdynia.pl>
Cc:        freebsd-hackers@freebsd.org, Brandon Falk <bfalk_bsd@brandonfa.lk>
Subject:   Re: SMP Version of tar
Message-ID:  <324B736D-8961-4E44-A212-2ECF3E60F2A0@kientzle.com>
In-Reply-To: <alpine.BSF.2.00.1210071859430.15957@wojtek.tensor.gdynia.pl>
References:  <5069C9FC.6020400@brandonfa.lk> <alpine.BSF.2.00.1210071859430.15957@wojtek.tensor.gdynia.pl>

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On Oct 7, 2012, at 10:00 AM, Wojciech Puchar wrote:

>> I would be willing to work on a SMP version of tar (initially just =
gzip or something).
>>=20
>> I don't have the best experience in compression, and how to =
multi-thread it, but I think I would be able to learn and help out.
>=20
> gzip cannot - it is single stream.

gunzip commutes with cat, so gzip
compression can be multi-threaded
by compressing separate blocks and
concatenating the result.

For proof, look at Mark Adler's pigz
program, which does exactly this.

GZip decompression is admittedly trickier.


> bzip2 - no idea

bzip2 is block oriented and can be multi-threaded for both compression =
and decompression.


Tim




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