Protocol

protocol defines macro and constant parameters used in XSched, also provide some functions to get these constant parameters.

It also defines configurations that can be changed by command export Name=VALUE in shell.

XQueue configuration

Name	Type	Range	Default Value	Description
XSCHED_AUTO_XQUEUE	string	ON/OFF	OFF	If it automatically creates XQueue when creating a hardware queue.
XSCHED_AUTO_XQUEUE_LEVEL	int	[1, 3]	1	XQueue preemption level.
XSCHED_AUTO_XQUEUE_THRESHOLD	int	[1, MAX_INT64]	16	Maximum number of commands for In-flight status(commands that can be executed simultaneously in a hardware queue).
XSCHED_AUTO_XQUEUE_BATCH_SIZE	int	[1, threshold]	8	TODO
XSCHED_AUTO_XQUEUE_PRIORITY	int	[-256, 255]	0	Default priority of "HPF" policy
XSCHED_AUTO_XQUEUE_UTILIZATION	int	[0, 100]	100	Default utilization of "UP" and "PUP" policy
XSCHED_AUTO_XQUEUE_TIMESLICE	int	[100, 100000]	5000	Default time slice of "RR" policy

Scheduler configuration

Change default scheduler type of processes by setting XSCHED_SCHEDULER to type name. The default value is GLB.

Value	Full Name	Transparency	Description
LCL	Local Scheduler	✅	Process has its own scheduler, it only schedules xqueues created by itself.
GLB	Global Scheduler	✅	Process use global scheduler in XServer.
APP	Application Managed	❌	There is no scheduler in process, application needs to use XQueue API to manage xqueues.

Policy configuration

Change default scheduling policy in XServer by setting XSCHED_POLICY to policy name. The default value is HPF.

Value	Full Name
HPF	Highest Priority First
UP	Utilization Partition
PUP	Process Utilization Partition
KEDF	K-Earliest Deadline First
LAX	Laxity-based

(refering to policies)