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Slow boot times as more CPU’s are added to the guest OS

PostPosted: 1. Dec 2011, 23:48
by lanbrown
I'm running Solaris 11 on a Sun x4470M2 server with dual Intel Xeon E7-4870, 10-core 2.4 GHz processors. I have VirtualBox 4.1.6 installed and when configuring a guest if I assign one CPU to it, it boots normally. If I assign 2, it takes a little longer, if I assign four, it takes even more time. If I assign 32, it will take over an hour to boot whereas if I assign a single CPU, it is boots in less than 2 minutes. I currently have it set to 16 and even that took about 10 to 15 minutes. The OS is CentOS 6.

Do the developers need any logs to see why it takes so long for it to boot as more CPU’s are added?

Re: Slow boot times as more CPU’s are added to the guest OS

PostPosted: 12. Dec 2011, 15:24
by klaus
Since no host OS has gang scheduling the efficiency of SMP goes down quite fast with the number of vCPUs, especially if the workload in the guest OS triggers lots of cross-CPU synchronization. For number crunching SMP can scale quite well...

Re: Slow boot times as more CPU’s are added to the guest OS

PostPosted: 12. Dec 2011, 19:44
by lanbrown
So taking an hour to boot is normal? The Guest essentially is doing very little work at this point. Once it is up, you can load the vCPU's and it runs fine, booting just takes ages. Using other VM solutions work far better than VirtualBox in boot times; they boot extremely fast; typically quicker as the platform is virtualized and you don't have all the POST sequences to get in the way to slow things down.

Re: Slow boot times as more CPU’s are added to the guest OS

PostPosted: 12. Dec 2011, 19:49
by klaus
No, it's not normal... the SMP overhead is usually much lower.

Re: Slow boot times as more CPU’s are added to the guest OS

PostPosted: 27. Dec 2011, 21:06
by lanbrown
Can I gather any logs so they can be passed on to the dev team? Once it is booted the processing power is pretty much on par with a dedicated box. The booting is just horrendous though.

Re: Slow boot times as more CPU’s are added to the guest OS

PostPosted: 10. Jan 2012, 17:23
by Ramshankar
The log would be a start. we'll probably have to test and profile it here. So please upload the log.