snapshot pv multi-threading

pv_threading.py

# ...
from multiprocessing import Process, Manager

def get(d, pv_name, size, start, pid):
    pv = PV(pv_name)
    if pv.wait_for_connection(timeout=1.0):
        d[pv_name] = pv.get(use_monitor=False)
    else:
        d[pv_name] = 'not connected'
    if len(d) == size:
        print int(round((time.time() - start) * 1000))
        os.kill(pid, signal.SIGTERM)

# ...
size = len(pv_list)
manager = Manager()
d = manager.dict()
start = time.time()
pid = os.getpid()

for pv_name in pv_list:
    p = Process(target=get, args=(d, pv_name, size, start, pid))
    p.start()

time.sleep(30)