diff options
Diffstat (limited to 'docs/src/interface/scheduling.tex')
| -rw-r--r-- | docs/src/interface/scheduling.tex | 268 |
1 files changed, 0 insertions, 268 deletions
diff --git a/docs/src/interface/scheduling.tex b/docs/src/interface/scheduling.tex deleted file mode 100644 index fd540e8442..0000000000 --- a/docs/src/interface/scheduling.tex +++ /dev/null @@ -1,268 +0,0 @@ -\chapter{Scheduling API} - -The scheduling API is used by both the schedulers described above and should -also be used by any new schedulers. It provides a generic interface and also -implements much of the ``boilerplate'' code. - -Schedulers conforming to this API are described by the following -structure: - -\begin{verbatim} -struct scheduler -{ - char *name; /* full name for this scheduler */ - char *opt_name; /* option name for this scheduler */ - unsigned int sched_id; /* ID for this scheduler */ - - int (*init_scheduler) (); - int (*alloc_task) (struct task_struct *); - void (*add_task) (struct task_struct *); - void (*free_task) (struct task_struct *); - void (*rem_task) (struct task_struct *); - void (*wake_up) (struct task_struct *); - void (*do_block) (struct task_struct *); - task_slice_t (*do_schedule) (s_time_t); - int (*control) (struct sched_ctl_cmd *); - int (*adjdom) (struct task_struct *, - struct sched_adjdom_cmd *); - s32 (*reschedule) (struct task_struct *); - void (*dump_settings) (void); - void (*dump_cpu_state) (int); - void (*dump_runq_el) (struct task_struct *); -}; -\end{verbatim} - -The only method that {\em must} be implemented is -{\tt do\_schedule()}. However, if there is not some implementation for the -{\tt wake\_up()} method then waking tasks will not get put on the runqueue! - -The fields of the above structure are described in more detail below. - -\subsubsection{name} - -The name field should point to a descriptive ASCII string. - -\subsubsection{opt\_name} - -This field is the value of the {\tt sched=} boot-time option that will select -this scheduler. - -\subsubsection{sched\_id} - -This is an integer that uniquely identifies this scheduler. There should be a -macro corrsponding to this scheduler ID in {\tt <xen/sched-if.h>}. - -\subsubsection{init\_scheduler} - -\paragraph*{Purpose} - -This is a function for performing any scheduler-specific initialisation. For -instance, it might allocate memory for per-CPU scheduler data and initialise it -appropriately. - -\paragraph*{Call environment} - -This function is called after the initialisation performed by the generic -layer. The function is called exactly once, for the scheduler that has been -selected. - -\paragraph*{Return values} - -This should return negative on failure --- this will cause an -immediate panic and the system will fail to boot. - -\subsubsection{alloc\_task} - -\paragraph*{Purpose} -Called when a {\tt task\_struct} is allocated by the generic scheduler -layer. A particular scheduler implementation may use this method to -allocate per-task data for this task. It may use the {\tt -sched\_priv} pointer in the {\tt task\_struct} to point to this data. - -\paragraph*{Call environment} -The generic layer guarantees that the {\tt sched\_priv} field will -remain intact from the time this method is called until the task is -deallocated (so long as the scheduler implementation does not change -it explicitly!). - -\paragraph*{Return values} -Negative on failure. - -\subsubsection{add\_task} - -\paragraph*{Purpose} - -Called when a task is initially added by the generic layer. - -\paragraph*{Call environment} - -The fields in the {\tt task\_struct} are now filled out and available for use. -Schedulers should implement appropriate initialisation of any per-task private -information in this method. - -\subsubsection{free\_task} - -\paragraph*{Purpose} - -Schedulers should free the space used by any associated private data -structures. - -\paragraph*{Call environment} - -This is called when a {\tt task\_struct} is about to be deallocated. -The generic layer will have done generic task removal operations and -(if implemented) called the scheduler's {\tt rem\_task} method before -this method is called. - -\subsubsection{rem\_task} - -\paragraph*{Purpose} - -This is called when a task is being removed from scheduling (but is -not yet being freed). - -\subsubsection{wake\_up} - -\paragraph*{Purpose} - -Called when a task is woken up, this method should put the task on the runqueue -(or do the scheduler-specific equivalent action). - -\paragraph*{Call environment} - -The task is already set to state RUNNING. - -\subsubsection{do\_block} - -\paragraph*{Purpose} - -This function is called when a task is blocked. This function should -not remove the task from the runqueue. - -\paragraph*{Call environment} - -The EVENTS\_MASTER\_ENABLE\_BIT is already set and the task state changed to -TASK\_INTERRUPTIBLE on entry to this method. A call to the {\tt - do\_schedule} method will be made after this method returns, in -order to select the next task to run. - -\subsubsection{do\_schedule} - -This method must be implemented. - -\paragraph*{Purpose} - -The method is called each time a new task must be chosen for scheduling on the -current CPU. The current time as passed as the single argument (the current -task can be found using the {\tt current} macro). - -This method should select the next task to run on this CPU and set it's minimum -time to run as well as returning the data described below. - -This method should also take the appropriate action if the previous -task has blocked, e.g. removing it from the runqueue. - -\paragraph*{Call environment} - -The other fields in the {\tt task\_struct} are updated by the generic layer, -which also performs all Xen-specific tasks and performs the actual task switch -(unless the previous task has been chosen again). - -This method is called with the {\tt schedule\_lock} held for the current CPU -and local interrupts disabled. - -\paragraph*{Return values} - -Must return a {\tt struct task\_slice} describing what task to run and how long -for (at maximum). - -\subsubsection{control} - -\paragraph*{Purpose} - -This method is called for global scheduler control operations. It takes a -pointer to a {\tt struct sched\_ctl\_cmd}, which it should either -source data from or populate with data, depending on the value of the -{\tt direction} field. - -\paragraph*{Call environment} - -The generic layer guarantees that when this method is called, the -caller selected the correct scheduler ID, hence the scheduler's -implementation does not need to sanity-check these parts of the call. - -\paragraph*{Return values} - -This function should return the value to be passed back to user space, hence it -should either be 0 or an appropriate errno value. - -\subsubsection{sched\_adjdom} - -\paragraph*{Purpose} - -This method is called to adjust the scheduling parameters of a particular -domain, or to query their current values. The function should check -the {\tt direction} field of the {\tt sched\_adjdom\_cmd} it receives in -order to determine which of these operations is being performed. - -\paragraph*{Call environment} - -The generic layer guarantees that the caller has specified the correct -control interface version and scheduler ID and that the supplied {\tt -task\_struct} will not be deallocated during the call (hence it is not -necessary to {\tt get\_task\_struct}). - -\paragraph*{Return values} - -This function should return the value to be passed back to user space, hence it -should either be 0 or an appropriate errno value. - -\subsubsection{reschedule} - -\paragraph*{Purpose} - -This method is called to determine if a reschedule is required as a result of a -particular task. - -\paragraph*{Call environment} -The generic layer will cause a reschedule if the current domain is the idle -task or it has exceeded its minimum time slice before a reschedule. The -generic layer guarantees that the task passed is not currently running but is -on the runqueue. - -\paragraph*{Return values} - -Should return a mask of CPUs to cause a reschedule on. - -\subsubsection{dump\_settings} - -\paragraph*{Purpose} - -If implemented, this should dump any private global settings for this -scheduler to the console. - -\paragraph*{Call environment} - -This function is called with interrupts enabled. - -\subsubsection{dump\_cpu\_state} - -\paragraph*{Purpose} - -This method should dump any private settings for the specified CPU. - -\paragraph*{Call environment} - -This function is called with interrupts disabled and the {\tt schedule\_lock} -for the specified CPU held. - -\subsubsection{dump\_runq\_el} - -\paragraph*{Purpose} - -This method should dump any private settings for the specified task. - -\paragraph*{Call environment} - -This function is called with interrupts disabled and the {\tt schedule\_lock} -for the task's CPU held. |