Re: [libvirt PATCH 00/11] qemu: introduce a per-VM event loop thread

On 2/14/20 1:51 PM, Daniel P. Berrangé wrote: > This series changes the way we manage the QEMU monitor and > QEMU agent, such that all I/O is processed by a dedicated > event loop thread. > > Many times in the past years people are reported issues > where long running monitor event callbacks block the main > libvirtd event loop for an unacceptably long period of > time. In the best case, this delays other work being > completed, but in bad cases it leads to mgmt app failures > when keepalive times trigger a client disconnect. > > With this series, when we spawn QEMU, we also spawn a > dedicated thread running a GMainLoop instance. Then QEMU > monitor and QEMU agent UNIX sockets are switched to use > GMainContext for events instead of the traditional libvirt > event loop APIs. We kill off the event thread when we see > EOF on the QEMU monitor during shutdown. > > The cost of this approach is one extra thread per VM, > which incurs a new OS process and a new stack allocation. > > The QEMU driver already delegates some QMP event handling > to a thread pool for certain types of event. This was a > previous hack to mitigate the impact on the main event > loop. It is likely that we can remove this thread pool > from the QEMU driver & rely on the per-VM event threads > to do all the work. This will, however, require careful > analysis of each handler we pushed into the thread pool > to make sure its work doesn't have a dependency on the > event loop running in parallel. > > This should also eliminate the need to have the libvirt > event loop registered when using the embedded QEMU driver. > This has not yet been validated, however, so it is left > for a future patch to relax the constraint. > > Daniel P. Berrangé (11): > qemu: drop support for agent connections on PTYs > qemu: drop ability to open monitor from FD > src: set the OS level thread name > src: improve thread naming with human targetted names > src: introduce an abstraction for running event loops > qemu: start/stop an event loop thread for domains > qemu: start/stop an event thread for QMP probing > tests: start/stop an event thread for QEMU monitor/agent tests > qemu: convert monitor to use the per-VM event loop > qemu: fix variable naming in agent code > qemu: convert agent to use the per-VM event loop > > po/POTFILES.in | 1 + > src/libvirt_private.syms | 6 + > src/libxl/libxl_domain.c | 10 +- > src/libxl/libxl_migration.c | 23 +- > src/lxc/lxc_fuse.c | 4 +- > src/node_device/node_device_udev.c | 7 +- > src/nwfilter/nwfilter_dhcpsnoop.c | 11 +- > src/nwfilter/nwfilter_learnipaddr.c | 10 +- > src/qemu/qemu_agent.c | 634 ++++++++++++++-------------- > src/qemu/qemu_agent.h | 1 + > src/qemu/qemu_domain.c | 33 ++ > src/qemu/qemu_domain.h | 6 + > src/qemu/qemu_driver.c | 3 +- > src/qemu/qemu_migration.c | 8 +- > src/qemu/qemu_monitor.c | 155 +++---- > src/qemu/qemu_monitor.h | 8 +- > src/qemu/qemu_process.c | 61 ++- > src/qemu/qemu_process.h | 2 + > src/remote/remote_daemon.c | 9 +- > src/rpc/virnetserver.c | 9 +- > src/storage/storage_backend_scsi.c | 4 +- > src/storage/storage_driver.c | 4 +- > src/util/Makefile.inc.am | 2 + > src/util/vircommand.c | 5 +- > src/util/vireventthread.c | 175 ++++++++ > src/util/vireventthread.h | 31 ++ > src/util/virfdstream.c | 10 +- > src/util/virnodesuspend.c | 8 +- > src/util/virthread.c | 44 +- > src/util/virthread.h | 4 +- > src/util/virthreadpool.c | 14 +- > src/util/virthreadpool.h | 2 +- > tests/qemumonitortestutils.c | 15 + > 33 files changed, 832 insertions(+), 487 deletions(-) > create mode 100644 src/util/vireventthread.c > create mode 100644 src/util/vireventthread.h > I've ACKed the first four patches which can be pushed independently. Do you want me to continue or will you resend v2 starting from patch 05/11?