KVM call minutes for May 25

KVM call minutes for May 25

[Chris Wright]

Generic Asynchronous task offloading
- keep vcpu thread from blocking
- generic approach is useful, comes down to specifics
  - e.g. what is done in worker threads, how locking is handled
- offload blocking work to worker threads
- need to make device model reentrant 
  - can be simple w/ lock per device, but needs finer grained to be perfromant
  - but needs
- thread pool should be relatively easy to merge
- two alternatives for virtfs
  - one full request in thread, one that does syscalls asynchronously
  - need to have something demonstrably better to make threading acceptable
- complexity of state machine vs. locking
  - performance difference at the end (e.g. coarse grained locking
    doesn't fully allow for parallel execution)
- lapic needs to be reentrant
  - in qemu lapic should show off the benefit very well
- hpet would also benefit from being threaded
- multiple threads per device (needs device specific locking)
  - qxl, scsi, virtfs...
- push global lock down to pio/mmio dispatch
  - audit for global qemu state changes done w/in device
- anthony will set up wiki page to describe making device models reentrant
  - looking for volunteers!