kernel/parallel_xz.sh

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#!/bin/sh
# Reads filenames on stdin, xz-compresses each in place.
# Not optimal for "compress relatively few, large files" scenario!
# How many xz's to run in parallel:
procgroup=""
while test "$#" != 0; do
# Get it from -jNUM
N="${1#-j}"
if test "$N" = "$1"; then
# Not -j<something> - warn and ignore
echo "parallel_xz: warning: unrecognized argument: '$1'"
else
procgroup="$N"
fi
shift
done
#This seems to cause problems with large numbers
if (( $procgroup > 8 )); then
procgroup=8
fi
# If told to use only one cpu:
test "$procgroup" || exec xargs -r xz
test "$procgroup" = 1 && exec xargs -r xz
# xz has some startup cost. If files are really small,
# this cost might be significant. To combat this,
# process several files (in sequence) by each xz process via -n 16:
exec xargs -r -n 16 -P $procgroup xz