Date: Wed, 4 Nov 2009 06:05:44 +0300 From: Eygene Ryabinkin <rea-fbsd@codelabs.ru> To: Mel Flynn <mel.flynn+fbsd.hackers@mailing.thruhere.net> Cc: freebsd-hackers@freebsd.org Subject: Re: Issue with grep -i (on i386 only?) Message-ID: <T7DtLCOP0cwiekv/7ybsxY3l5dQ@7ANLw7WpNQUEViOFvqmcIRbmcl4> In-Reply-To: <200911032122.28905.mel.flynn%2Bfbsd.hackers@mailing.thruhere.net> References: <200911032122.28905.mel.flynn%2Bfbsd.hackers@mailing.thruhere.net>
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Mel, good day.
Tue, Nov 03, 2009 at 09:22:28PM +0100, Mel Flynn wrote:
> So on the laptop I modified the testscript as it is attached now and
> while there is still a significant delay, the wallclock time is less
> then half, when the expression is rewritten with the same meaning:
> =>>> 16777216
> =>>> fgrep
> 0.04 real 0.03 user 0.00 sys
> 0.05 real 0.03 user 0.01 sys
> 0.02 real 0.00 user 0.00 sys
> =>>> pcregrep
> 0.26 real 0.21 user 0.02 sys
> 0.26 real 0.22 user 0.02 sys
> 0.44 real 0.35 user 0.01 sys
> =>>> grep
> 0.04 real 0.04 user 0.00 sys
> 4.45 real 4.15 user 0.01 sys
> 2.00 real 1.81 user 0.00 sys <-- [fF][Oo][Oo]
Just did a quick test on the 8.0-RC2/i386 with very old Athlon processor:
-----
=>>> 16777216
=>>> fgrep
0,09 real 0,04 user 0,05 sys
0,18 real 0,06 user 0,03 sys
0,05 real 0,01 user 0,04 sys
=>>> pcregrep
0,47 real 0,29 user 0,07 sys
0,52 real 0,33 user 0,07 sys
0,77 real 0,45 user 0,03 sys
=>>> grep
0,09 real 0,08 user 0,01 sys
0,10 real 0,04 user 0,05 sys
0,23 real 0,12 user 0,03 sys
-----
Pattern for the plain 'grep' is stable: first and second variants always
give the same time within a 0.01 second variation and the last variant
gives 2x slowdown.
I tried sizes up to the 64M -- the pattern stays. The same stuff for
the amd64, so in my case I don't see the difference in behaviour. So,
maybe, the problem isn't 32 vs 64 but lies somewhere else.
> attached a little test script for grep's -i performance.
Some notes about the script, especially if (or some variant of it)
will be included to the testing framework.
> #!/bin/sh
> # vim: ts=4 sw=4 noet tw=78 ai
>
> PCREGREP=`which pcregrep`
> BSDGREP=`which bsdgrep`
> [ -n ${PCREGREP} ] && PCREGREP=`basename ${PCREGREP}`
> [ -n ${BSDGREP} ] && BSDGREP=`basename ${BSDGREP}`
You'll want '[ -n "${PCREGREP}" ] && ...' (with quoted variable) to
really achieve the kind of test you wanted.
> if [ ! -x /usr/bin/jot ]; then
> echo "Need jot"
> exit 1
> fi
> if [ ! -x /usr/bin/rs ]; then
> echo "Need rs"
> exit 1
> fi
Probably this is better be written as
-----
for prog in jot rs; do
if [ -z "`which "$prog"`" ]; then
echo "Need $prog"
exit 1
fi
done
-----
because the latter code uses unqualified 'jot' and 'rs'.
> for b in ${BYTES}; do
> TMPFILE=`mktemp -t ${me}`
> if [ ! -f ${TMPFILE} ]; then
> echo Can\'t create tmp files in ${TMPDIR:="/tmp"}
> exit 2
> fi
> jot -r -c ${b} a z |rs -g 0 20 > ${TMPFILE}
> echo "=>>> ${b}"
> for prog in fgrep ${PCREGREP} ${BSDGREP} grep ; do
> echo " =>>> ${prog}"
> /usr/bin/time ${prog} foo ${TMPFILE} >/dev/null
> /usr/bin/time ${prog} -i foo ${TMPFILE} >/dev/null
> /usr/bin/time ${prog} '[fF][Oo][Oo]' ${TMPFILE} >/dev/null
> done
> rm ${TMPFILE}
> done
Most likely, it is better to create the temporary file only once
and to trap the signals with the file removal -- this will handle
the cases when user presses ^C during the execution -- temporary
file should be cleaned in this case. The code is simple:
-----
TMPFILE=`mktemp -t ${me}`
if [ ! -f ${TMPFILE} ]; then
echo "Can't create tmp file in ${TMPDIR:=/tmp}"
exit 2
fi
trap 'rm -f "${TMPFILE}"' 0 1 2 3 15
-----
Attaching modified version with the bonus -- 'K' and 'M' size prefixes:
it was boring to specify many digits when I had played with sizes ;))
--
Eygene
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