qsbench, interesting results

[Lorenzo Allegrucci]

qsbench is a VM benchmark based on sorting a large array
by quick sort.
http://web.tiscali.it/allegrucci/qsbench-1.0.0.tar.gz

Below are some results of qsbench sorting a 350Mb array
on a 256+400Mb RAM+swap machine.
Tested kernels: 2.4.19, 2.5.38 and 2.5.39
All runs made with the same default seed, to compare
apples with apples :)
I used /usr/bin/time because it gives better statistics
such as major and minor page faults etc.
(Sorry for >72 cols).

2.4.19
bash-2.05# /usr/bin/time ./qsbench -m 350
46.29user 3.54system 2:34.66elapsed 32%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (24739major+370199minor)pagefaults 0swaps
bash-2.05# /usr/bin/time ./qsbench -m 350
46.57user 3.27system 2:35.73elapsed 32%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (24493major+370706minor)pagefaults 0swaps
bash-2.05# /usr/bin/time ./qsbench -m 350
46.61user 3.09system 2:35.91elapsed 31%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (24560major+370571minor)pagefaults 0swaps

Perfectly reproducible performance.

2.5.38
bash-2.05# /usr/bin/time ./qsbench -m 350
ERROR: i = 7766682
 *** WARNING ***  1 errors.
47.11user 3.57system 3:42.19elapsed 22%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (39875major+439626minor)pagefaults 0swaps
bash-2.05# /usr/bin/time ./qsbench -m 350
46.80user 3.68system 3:42.20elapsed 22%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (39336major+441350minor)pagefaults 0swaps
bash-2.05# /usr/bin/time ./qsbench -m 350
46.87user 3.70system 3:44.50elapsed 22%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (39926major+440091minor)pagefaults 0swaps

This is interesting, qsbench got an array not "quite" sorted.
I have run qsbench a lot of times in the past on many kernels
and I have never seen such error.
I don't think it's my hardware fault so I would like to know
if somebody can reproduce it.
Performance is worse than 2.4.19

2.5.39
bash-2.05# /usr/bin/time ./qsbench -m 350
46.94user 4.41system 8:17.94elapsed 10%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (66343major+455167minor)pagefaults 0swaps
bash-2.05# /usr/bin/time ./qsbench -m 350
46.74user 4.64system 8:45.03elapsed 9%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (68600major+454782minor)pagefaults 0swaps
bash-2.05# /usr/bin/time ./qsbench -m 350
46.81user 4.31system 8:37.07elapsed 9%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (69090major+454355minor)pagefaults 0swaps

Big performance drop.

Comments?