[CentOS] Kernel ELsmp vs EL

Tue Sep 12 07:25:46 UTC 2006
Robert Stuart <r.stuart at qut.edu.au>

Hi John,

John Summerfield wrote:
> summer at 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 at 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 at ihbids /tmp# time ./bm.perl
uname -a
real    0m12.783s
user    0m12.765s
sys     0m0.002s
root at 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 at 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 at basilisk /tmp# time ./bm.perl

real    0m14.309s
user    0m14.095s
sys     0m0.121s
root at 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 at 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 at ihbids /tmp# dmesg |grep 'CPU: L'
CPU: L2 cache: 2048K
CPU: L2 cache: 2048K

Robert Stuart
Systems Administrator
Institute of Health and Biomedical Innovation