Re: [libvirt] Revisiting qemu monitor timeout on VM start

Hi All, Encountering a qemu monitor timeout when starting a VM has been discussed here before, e.g. https://www.redhat.com/archives/libvir-list/2014-January/msg00060.html https://www.redhat.com/archives/libvir-list/2014-January/msg00408.html Recently I've received reports of the same when starting large memory VMs backed by 1G huge pages. In one of the reports, Matt timed how long it takes to allocate 402GB worth of hugetlbfs pages (these are 1G pages, but the time is similar for 2M): real 105.47 user 0.05 sys 105.42 The time is spent entirely in the kernel zero'ing pages and as you can see it exceeds the 30 second monitor timeout in libvirt. Do folks have any suggestions on how to avoid the timeout? Obviously one solution is to introduce a knob in qemu.conf to control the timeout, as was proposed in the above threads. Another solution that came to mind is changing qemu to open the monitor earlier, making it available while the kernel is off scrubbing pages. I'm not familiar enough with qemu code to know if such a change is possible, but given the amount of initialization done in main() prior to calling mon_init_func(), my confidence in this idea is low. Perhaps someone more familiar with qemu initialization can comment on that. Thanks in advance for comments on these ideas or alternate proposals!