Hello, I see that in the xl binary in xen 4.13.0, the acquire_lock() and release_lock() functions are only called from create_domain() in xl_vmcontrol.c, so I assume the lock provides inter-PROCESS synchronization in the case that multiple instances of xl are running and creating multiple domains concurrently.
However, this lock causes a bottleneck in the case that an xl restore process is restoring a DomU with a lot of memory. While the large amount of memory is being copied from the checkpoint file on disk to the physical machine's RAM, all other VM creation requests on the system are starved, leading to a performance loss. When I removed the lock, my testing of simultaneous creation of 2 DomU's concurrently worked and I did not see any issues. Does anyone know what shared resource these locks are guarding? Maybe we should be making the lock more granular. -- My Blog: http://www.neilscomputerblog.blogspot.com/ Twitter: @neilsikka
