Hi John,
John Summerfield wrote:
summer@Mopoke:~> time bm.perl&time bm.perl&wait [1] 3480 [2] 3481
real 0m23.935s user 0m23.689s sys 0m0.004s
real 0m25.906s user 0m24.746s sys 0m0.004s [1]- Done time bm.perl [2]+ Done time bm.perl
What are the results for a single "time bm.perl" ?
These are my results, first on a HT P4: root@ihbids /tmp# uname -a Linux ihbids.ihbi.qut.edu.au 2.6.9-42.0.2.ELsmp #1 SMP Wed Aug 23 00:17:26 CDT 2006 i686 i686 i386 GNU/Linux root@ihbids /tmp# time ./bm.perl uname -a real 0m12.783s user 0m12.765s sys 0m0.002s root@ihbids /tmp# time ./bm.perl & time ./bm.perl & wait [1] 29798 [2] 29799
real 0m21.422s user 0m21.395s sys 0m0.003s [1]- Done time ./bm.perl
real 0m21.589s user 0m20.467s sys 0m0.003s [2]+ Done time ./bm.perl
One a system with real SMP (Opteron, dual core, dual socket): root@basilisk /tmp# uname -a Linux basilisk.ihbi.qut.edu.au 2.6.9-34.0.2.ELsmp #1 SMP Fri Jul 7 18:22:55 CDT 2006 x86_64 x86_64 x86_64 GNU/Linux root@basilisk /tmp# time ./bm.perl
real 0m14.309s user 0m14.095s sys 0m0.121s root@basilisk /tmp# time ./bm.perl & time ./bm.perl & wait [1] 26588 [2] 26589
real 0m14.232s user 0m14.178s sys 0m0.001s [1]- Done time ./bm.perl
real 0m14.256s user 0m14.194s sys 0m0.026s [2]+ Done time ./bm.perl root@basilisk /tmp# time ./bm.perl & time ./bm.perl & time ./bm.perl & time ./bm.perl & wait [1] 26592 [2] 26593 [3] 26594 [4] 26595 real 0m14.164s user 0m14.125s sys 0m0.009s
real 0m14.597s user 0m14.149s sys 0m0.071s
real 0m15.020s user 0m14.335s sys 0m0.030s [1] Done time ./bm.perl [3]- Done time ./bm.perl [4]+ Done time ./bm.perl
real 0m15.143s user 0m14.168s sys 0m0.196s [2]+ Done time ./bm.perl
I believe my results show that HT does almost nothing at all. The P4 box does seem to have HT enabled - it is showing two cpus in /proc/cpuinfo and: root@ihbids /tmp# dmesg |grep 'CPU: L' CPU: L2 cache: 2048K CPU: L2 cache: 2048K
Regards Robert