I'm seeing huge discrepancies in grep speed between my Opteron box and P4 boxes. The Opteron box: ---------------- Dual Opteron 248, 2.2GHz, 1MB cache, 8GB memory, RHEL4 ls1_tsh> uname -a Linux ls1.lmb.internal 2.6.9-22.0.1.ELsmp #1 SMP Tue Oct 18 18:39:02 EDT 2005 x86_64 x86_64 x86_64 GNU/Linux ls1_tsh> grep -V grep (GNU grep) 2.5.1 grepping thro an 800 MB file: ls1_tsh> time grep rubbishrubbish /tshgrp0/tsh/junkjunk 41.618u 1.263s 0:43.30 99.0% 0+0k 0+0io 0pf+0w ls1_tsh> time grep rubbishrubbish /tshgrp0/tsh/junkjunk 41.675u 1.477s 0:43.54 99.0% 0+0k 0+0io 0pf+0w ls1_tsh> ls -l /tshgrp0/tsh/junkjunk -rw-r--r-- 1 tsh tsh 869243540 Sep 5 13:13 /tshgrp0/tsh/junkjunk I'm certain the file is all stored in cache during this, and that no disk accesses are taking place, because: 1. 'top' shows grep at 99.9% cpu 2. iostat on the disk in question shows zero activity. The P4 box: ----------- Monocore P4, 3.4GHz, 1MB cache, 2GB memory, FC3. fm22_tsh> uname -a Linux fm22.lmb.internal 2.6.11-1.35_FC3 #1 Mon Jun 13 00:52:08 EDT 2005 i686 i686 i386 GNU/Linux fm22_tsh> grep -V grep (GNU grep) 2.5.1 fm22_tsh> time grep rubbishrubbish /scr0/tsh/junkjunk 0.272u 0.318s 0:00.59 98.3% 0+0k 0+0io 0pf+0w fm22_tsh> time grep rubbishrubbish /scr0/tsh/junkjunk 0.311u 0.281s 0:00.59 100.0% 0+0k 0+0io 0pf+0w fm22_tsh> ls -l /scr0/tsh/junkjunk -rw-r--r-- 1 tsh users 869243540 Sep 5 14:29 /scr0/tsh/junkjunk This is indicating that grep on the Opteron is *forty* times slower than on the P4. Any ideas why this might be? 64-bit nasties in grep? Has anyone else seen this? Cheers, Terry
