Measure the cost of greenlet switching.

switchbench.py

import gevent
import sys

N = int(sys.argv[1])
M = int(sys.argv[2])

def sleeper(n):
    for i in xrange(N):
        #print(n)
        gevent.sleep(0)

def sleeper2(n):
    hub = gevent.get_hub()
    idle = hub.loop.idle(1)
    wait = hub.wait
    for i in xrange(N):
        #print(n)
        wait(idle)

greenlets = [gevent.spawn(sleeper2, i) for i in xrange(M)]
gevent.joinall(greenlets)

In my environment,

$ time python switchbench.py 1000 1000
real    0m11.314s
user    0m11.241s
sys 0m0.056s

sleeper2 inlined gevent.sleep(). This makes significant speedup.

$ time python switchbench.py 1000 1000
real    0m7.891s
user    0m7.844s
sys 0m0.032s

Real Python application has more Python code. So the cost of greenlet switching is small relatively.