From 8dbecc00d5f97d9809dcc6f0e80f1e2637e11351 Mon Sep 17 00:00:00 2001 From: George Dunlap Date: Mon, 1 Oct 2012 17:49:01 +0100 Subject: docs: Document scheduler-related Xen command-line options Signed-off-by: George Dunlap Acked-by: Ian Campbell Committed-by: Ian Jackson --- docs/misc/xen-command-line.markdown | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) (limited to 'docs/misc') diff --git a/docs/misc/xen-command-line.markdown b/docs/misc/xen-command-line.markdown index 716f3692c2..5b18e10311 100644 --- a/docs/misc/xen-command-line.markdown +++ b/docs/misc/xen-command-line.markdown @@ -740,12 +740,34 @@ Choose the default scheduler. ### sched\_credit\_tslice\_ms > `= ` +Set the timeslice of the credit1 scheduler, in milliseconds. The +default is 30ms. Reasonable values may include 10, 5, or even 1 for +very latency-sensitive workloads. + ### sched\_ratelimit\_us > `= ` +In order to limit the rate of context switching, set the minimum +amount of time that a vcpu can be scheduled for before preempting it, +in microseconds. The default is 1000us (1ms). Setting this to 0 +disables it altogether. + ### sched\_smt\_power\_savings > `= ` +Normally Xen will try to maximize performance and cache utilization by +spreading out vcpus across as many different divisions as possible +(i.e, numa nodes, sockets, cores threads, &c). This often maximizes +throughput, but also maximizes energy usage, since it reduces the +depth to which a processor can sleep. + +This option inverts the logic, so that the scheduler in effect tries +to keep the vcpus on the smallest amount of silicon possible; i.e., +first fill up sibling threads, then sibling cores, then sibling +sockets, &c. This will reduce performance somewhat, particularly on +systems with hyperthreading enabled, but should reduce power by +enabling more sockets and cores to go into deeper sleep states. + ### serial\_tx\_buffer > `= ` -- cgit v1.2.3