SMP doesn't scale correctly
Posted: 2. Nov 2009, 17:15
Hi,
my host is Vista x64 with Quad Core, guest is Centos 5.3 32-bit version with 4 vCPU. On guest I'm running make for program compilation. I'm changing the number of concurrent jobs and measuring execute time. This are results, time in seconds:
There is something wrong with SMP. Using more then 2 vCPU concurrently increase execute time compared to single vCPU.
For comparison, similar test on VB and RedHat 7.3 with kernel 2.4 gives results as expected. Also VMware and Centos 5.3 scale correctly up to 4 vCPU.
I'm using VirtualBox 3.0.10 but the previous versions behave the same. Any idea what is wrong? I tried to add boot option divider=10 but it changed nothing.
my host is Vista x64 with Quad Core, guest is Centos 5.3 32-bit version with 4 vCPU. On guest I'm running make for program compilation. I'm changing the number of concurrent jobs and measuring execute time. This are results, time in seconds:
Code: Select all
jobs real user system
1 34 9 25
2 25 15 38
3 45 38 108
4 67 44 214
5 67 44 213For comparison, similar test on VB and RedHat 7.3 with kernel 2.4 gives results as expected. Also VMware and Centos 5.3 scale correctly up to 4 vCPU.
I'm using VirtualBox 3.0.10 but the previous versions behave the same. Any idea what is wrong? I tried to add boot option divider=10 but it changed nothing.