On 27/05/16 18:25, Paolo Bonzini wrote: > > On 27/05/2016 17:07, Sergey Fedorov wrote: >>>>>> 1. Make 'cpu->thread_kicked' access atomic >>>>>> 2. Remove global 'exit_request' and use per-CPU 'exit_request' >>>>>> 3. Change how 'current_cpu' is set >>>>>> 4. Reorganize round-robin CPU TCG thread function >>>>>> 5. Enable 'mmap_lock' for system mode emulation (do we really want >>>>>> this?) >>>> No, I don't think so. >>>> >>>>>> 6. Enable 'tb_lock' for system mode emulation >>>>>> 7. Introduce per-CPU TCG thread function >>>> At least 2/3/7 must be done at the same time, but I agree that this >>>> patch could use some splitting. :) >> Hmm, 2/3 do also change single-threaded CPU loop. I think they should >> apply separately from 7. > Reviewed the patch now, and I'm not sure how you can do 2/3 for the > single-threaded CPU loop. They could be moved out of cpu_exec and into > cpus.c (in a separate patch), but you need exit_request and > tcg_current_cpu to properly kick the single-threaded CPU loop out of > qemu_tcg_cpu_thread_fn.
Summarizing Paolo and my chat on IRC, we want run_on_cpu() to be served as soon as possible so that it would not block IO thread for too long. Removing global 'exit_request' would mean that a run_on_cpu() request from IO thread wouldn't be served until single-threaded CPU loop schedules the target CPU. This doesn't seem to be acceptable. NB: Calling run_on_cpu() for other CPU from the CPU thread would cause a deadlock in single-threaded round-robin CPU loop. Thanks, Sergey
