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Re: xz-5.2.2: No threaded compression




On 10/05/17 01:15, Yaakov Selkowitz wrote:
On 2017-05-09 18:02, David Stacey wrote:
The man page for xz suggests that threaded compression ought to be
available. However, when I run 'xz --threads=0 <file>' only one CPU core
is used. Is there a way that I can run parallel xz compression in Cygwin?

WFM.  Note from the manpage:

   -T threads, --threads=threads
       Specify the number of worker threads to use.  Setting threads to
       a  special value 0 makes xz use as many threads as there are CPU
       cores on the system.  The actual number of threads can  be less
       than  threads  if the input file is not big enough for threading
       with the given settings or if using more  threads  would exceed
       the memory usage limit.

That's helpful, thank you. The files I'm trying to compress are several GB, so I suppose I must be hitting the memory limit - which is surprising, given that I'm on a 64-bit system with a fair amount of RAM. I'll take a look at the source code and see if I can figure out what criteria it uses to enable or disable threaded compression.

Thanks again,

Dave.


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