kindly ping？ On 2021/7/30 21:10, Zheng Chuan wrote: > Hi, Steve > I have saw the discussion about the fork+exec mode below: > https://www.mail-archive.com/qemu-devel@nongnu.org/msg815956.html > > And I am still very curious and I want to discuss about the possibility to > support both fork+exec and exec in cpr framework. > > 1.Why > fork+exec could have some advantages and also drawbacks versus execvp() > directly. > Advantages > i) fork+exec give the chance to fallback to original process even after we do > exec which is important for workload seamless if any error happens. > ii) smaller downtime since we could remove the vm_start() downtime out of the > frozen window. > Drawbacks > i）need more codes to handle including fork，address/ports conflict between > parent and child. > ii）more complex life cycle management for the two processes. > > 2.How > The cpr framework is flexible and scalable, and maybe we can make use of most > codes to support both execvp and fork+exec mode. > However, we may need to do more work compared to execvp method. > i) do fork mode in a thread like migration thread > ii) make parent and child talk to each other through socket or anonymous pipe > iii）make use of sharing mechanism of fds in cpr framework including memfd, > vfio and devices fds > iv）deal with the conflict about the socket address and port like vnc （do by > reuse port and pass the different args by cprexec） > v) do life cycle managements for two qemu processes and need parent exit and > reconnection for the child at last by the management service > > Please tell me if I am missing something important:) >
-- Regards. Chuan
