[vbox-dev] Updating network interfaces list speed-up

[a.urakov at drweb.com]

Hello!

We would like to contribute to VirtualBox under MIT license. We want to 
suggest our changes for multiple VMs starting speed-up.

The basic idea is to take out getting of host interfaces from write lock 
on host object. When many VMs are starting at the same time then 
/FindHostNetworkInterfaceByName/ is called for every machine and it 
updates network interfaces. So if umount of VMs is large enough then 
execution time of this function greatly increases due to lock wait.

There are two /VBoxSVC/ logs in attach: before applying our changes and 
after it. In every case we started 80 VMs at the same time. Statistic of 
/FindHostNetworkInterfaceByName/ execution time before changes is:

Min: 0.38 s (nspr-31)
Med: 14.13 s (nspr-82)
Max: 37.70 s (nspr-188)
Avg: 15.07 s

Statistic after changes is:

Min: 1.12 s (nspr-85)
Med: 6.56 s (nspr-228)
Max: 17.27 s (nspr-7)
Avg: 5.82 s

Regards,
Alexander

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