Xen 4.2 will contain two new scheduling parameters for the credit1 scheduler which significantly increase its confurability and performance for cloud-based workloads:
ratelimit_us. This blog post describes what they do, and how to configure them for best performance.
The timeslice for the credit1 has historically been fixed at 30ms. This is actually a fairly long time — it’s great for computationally-intensive workloads, but not so good for latency-sensitive workloads, particularly ones involving network traffic or audio.
Xen 4.2 introduces the
tslice_ms parameter, which sets the timeslice of the scheduler in milliseconds. This can be set either using the Xen command-line option,
sched_credit_tslice_ms, or by using the new scheduling parameter interface to
# xl sched-credit -t [n]