From: Ariel Biener (ariel_at_nonexisting.hamakor.org.il)
Date: Tue 06 Jan 2004 - 03:56:43 IST
Hi,
I have spent about an hour diagnosing the following:
I have a passwd file, about 50,000 lines in length. I had a problem
with a script grepping something from it, and when debugging I found out
that:
Pentium4 Xeon, RedHat 9, latest RH kernel, fully updated system:
time grep : passwdfile > /dev/null
~1 minute, 12 seconds
Pentium4 Xeon, RedHat 7.2, latest RH kernel, fully updated system:
time grep : passwdfile > /dev/null
~0.04 seconds
Pentium3, RedHat 9, latest RH kernel, fully updated system:
time grep : passwdfile > /dev/null
~0.08 seconds
However, using `pcregrep' on the same systems yielded:
Pentium4 Xeon, RedHat 9, latest RH kernel, fully updated system:
time pcregrep : passwdfile > /dev/null
~0.05 seconds
Pentium4 Xeon, RedHat 7.2, latest RH kernel, fully updated system:
time grep : passwdfile > /dev/null
~0.08 seconds
Pentium3, RedHat 9, latest RH kernel, fully updated system:
time grep : passwdfile > /dev/null
~0.12 seconds
As you can see, there is a HUGE discrepancy between all the results
above and the Pentium4 Xeon, RedHat 9 `grep' case, about 900 times slower.
I tried recompiling the .src.rpm of the RedHat 9 grep locally on the
Xeon, but it yielded the same result.
As such, this appears (to me) to be some kind of a grep problem when
coupled with 2 Gigabytes of RAM, Xeon P4 CPU (with the HT on) on RedHat 9.
While I am researching some more on this, does any of you have any idea ?
My hunch is towards write(), since I also tested it with grep --mmap
(which uses mmap() instead of read() for reading) and it yielded the same
results.
--Ariel
-- Ariel Biener e-mail: ariel_at_post.tau.ac.il PGP(6.5.8) public key http://www.tau.ac.il/~ariel/pgp.html ================================================================= To unsubscribe, send mail to linux-il-request_at_linux.org.il with the word "unsubscribe" in the message body, e.g., run the command echo unsubscribe | mail linux-il-request_at_linux.org.il
This archive was generated by hypermail 2.1.7 : Tue 06 Jan 2004 - 04:06:41 IST