On Tue, 2010-04-06 at 15:55 -0500, Christoph Lameter wrote:
quoted text
> We cannot reproduce the issue here. Our tests here (dual quad dell) show a
> performance increase in hackbench instead.
I run hackbench on many machines. The regression exists on Nehalem machine
(dual sockets, 2*4*2 logical cpu) and a tigerton (4 socket, 4*4 logical cpu)
machines. I tried it on a dual quad core2 machine and it does like what you said.

The regression also exists on 2 new-generation Nehalem (dual socket 2*6*2 logical cpu)
machines.

It seems hyperthreading cpu has more chances to trigger it.

quoted text
> 
> Linux 2.6.33.2 #2 SMP Mon Apr 5 11:30:56 CDT 2010 x86_64 GNU/Linux
> ./hackbench 100 process 200000
> Running with 100*40 (== 4000) tasks.
> Time: 3102.142
> ./hackbench 100 process 20000
> Running with 100*40 (== 4000) tasks.
> Time: 308.731
> ./hackbench 100 process 20000
> Running with 100*40 (== 4000) tasks.
> Time: 311.591
> ./hackbench 100 process 20000
> Running with 100*40 (== 4000) tasks.
> Time: 310.200
> ./hackbench 10 process 20000
> Running with 10*40 (== 400) tasks.
> Time: 38.048
> ./hackbench 10 process 20000
> Running with 10*40 (== 400) tasks.
> Time: 44.711
> ./hackbench 10 process 20000
> Running with 10*40 (== 400) tasks.
> Time: 39.407
> ./hackbench 1 process 20000
> Running with 1*40 (== 40) tasks.
> Time: 9.411
> ./hackbench 1 process 20000
> Running with 1*40 (== 40) tasks.
> Time: 8.765
> ./hackbench 1 process 20000
> Running with 1*40 (== 40) tasks.
> Time: 8.822
> 
> Linux 2.6.34-rc3 #1 SMP Tue Apr 6 13:30:34 CDT 2010 x86_64 GNU/Linux
> ./hackbench 100 process 200000
> Running with 100*40 (== 4000) tasks.
> Time: 3003.578
> ./hackbench 100 process 20000
> Running with 100*40 (== 4000) tasks.
> Time: 300.289
> ./hackbench 100 process 20000
> Running with 100*40 (== 4000) tasks.
> Time: 301.462
> ./hackbench 100 process 20000
> Running with 100*40 (== 4000) tasks.
> Time: 301.173
> ./hackbench 10 process 20000
> Running with 10*40 (== 400) tasks.
> Time: 41.191
> ./hackbench 10 process 20000
> Running with 10*40 (== 400) tasks.
> Time: 41.964
> ./hackbench 10 process 20000
> Running with 10*40 (== 400) tasks.
> Time: 41.470
> ./hackbench 1 process 20000
> Running with 1*40 (== 40) tasks.
> Time: 8.829
> ./hackbench 1 process 20000
> Running with 1*40 (== 40) tasks.
> Time: 9.166
> ./hackbench 1 process 20000
> Running with 1*40 (== 40) tasks.
> Time: 8.681
> 
> 


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