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/* -*- C++ -*- */
// $Id$
// ============================================================================
//
// = LIBRARY
// ACE
//
// = FILENAME
// Sched_Params.h
//
// = CREATION DATE
// 28 January 1997
//
// = AUTHOR
// David Levine
//
// ============================================================================
#if !defined (ACE_SCHED_PARAMS_H)
#define ACE_SCHED_PARAMS_H
#include "ace/OS.h"
class ACE_Export ACE_Sched_Params
// = TITLE
// Container for scheduling-related parameters.
//
// = DESCRIPTION
// ACE_Sched_Params are passed via
// ACE_OS::sched_params () to the OS to specify scheduling
// parameters. These parameters include scheduling policy,
// such as FIFO, round-robin, or an implementation-defined
// "OTHER" (to which many systems default); priority; and
// a time-slice quantum for round-robin scheduling.
// A "scope" parameter specifies whether the ACE_Sched_Params
// applies to the current process, current lightweight process
// (LWP) (on Solaris), or current thread. Please see the "NOTE"
// below about not all combinations of parameters being legal
// on a particular platform.
//
// For the case of thread priorities, it is intended that
// ACE_OS::sched_params () usually be called from main () before
// any threads have been spawned.
// If spawned threads inherit their parent's priority (I think
// that's the default behavior for all of our platforms), then
// this sets the default base priority. Individual thread priorities
// can be adjusted as usual using ACE_OS::thr_prio () or via the
// ACE_Thread interface. See the parameter descriptions in the
// private: section below.
//
// NOTE: this class does not do any checking of parameters.
// It is just a container class. If it is constructed with values
// that are not supported on a platform, the call to
// ACE_OS::sched_params () will fail by returning -1 with EINVAL
// (available through ACE_OS::last_error ()).
// OS Scheduling parameters are complicated and often confusing. Many
// thanks to Thilo Kielmann <kielmann@informatik.uni-siegen.de> for his
// careful review of this class design, thoughtful comments, and
// assistance with implementation, especially for PTHREADS platforms.
// Please send any comments or corrections to the ACE developers.
{
public:
typedef int Policy;
// = Initialization and termination methods.
ACE_Sched_Params (const Policy policy,
const ACE_Sched_Priority priority,
const int scope = ACE_SCOPE_THREAD,
const ACE_Time_Value &quantum = ACE_Time_Value::zero);
// Constructor.
~ACE_Sched_Params (void);
// Termination.
// = Get/Set methods:
// = Get/Set policy
Policy policy (void) const;
void policy (const Policy);
// = Get/Set priority.
ACE_Sched_Priority priority (void) const;
void priority (const ACE_Sched_Priority);
// = Get/Set scope.
int scope (void) const;
void scope(const int);
// = Get/Set quantum.
const ACE_Time_Value &quantum (void) const;
void quantum (const ACE_Time_Value &);
// = Accessors for OS-specific priorities.
// These return ACE_SCHED_OTHER if the Policy value is invalid.
static int priority_min (const Policy,
const int scope = ACE_SCOPE_THREAD);
static int priority_max (const Policy,
const int scope = ACE_SCOPE_THREAD);
static int next_priority (const Policy,
const int priority,
const int scope = ACE_SCOPE_THREAD);
// The next higher priority. "Higher" refers to scheduling priority,
// not to the priority value itself. (On some platforms, higher scheduling
// priority is indicated by a lower priority value.) If "priority" is
// the highest priority (for the specified policy), then it is returned.
static int previous_priority (const Policy,
const int priority,
const int scope = ACE_SCOPE_THREAD);
// The previous, lower priority. "Lower" refers to scheduling priority,
// not to the priority value itself. (On some platforms, lower scheduling
// priority is indicated by a higher priority value.) If "priority" is
// the lowest priority (for the specified policy), then it is returned.
private:
Policy policy_;
// Scheduling policy.
ACE_Sched_Priority priority_;
// Default <priority_>: for setting the priority for the process, LWP,
// or thread, as indicated by the scope_ parameter.
int scope_;
// <scope_> must be one of the following:
// ACE_SCOPE_PROCESS: sets the scheduling policy for the
// process, and the process priority. On some platforms,
// such as Win32, the scheduling policy can _only_ be
// set at process scope.
// ACE_SCOPE_LWP: lightweight process scope, only used with
// Solaris threads.
// ACE_SCOPE_THREAD: sets the scheduling policy for the thread,
// if the OS supports it, such as with Posix threads, and the
// thread priority.
// NOTE: I don't think that these are the same as POSIX
// contention scope. POSIX users who are interested in,
// and understand, contention scope will have to set it
// by using system calls outside of ACE.
ACE_Time_Value quantum_;
// The <quantum_> is for time slicing. An ACE_Time_Value of 0 has
// special significance: it means time-slicing is disabled; with
// that, a thread that is running on a CPU will continue to run
// until it blocks or is preempted. Currently ignored if the OS
// doesn't directly support time slicing, such as on VxWorks, or
// setting the quantum (can that be done on Win32?).
};
#if defined (__ACE_INLINE__)
#include "ace/Sched_Params.i"
#endif /* __ACE_INLINE__ */
#endif /* ACE_SCHED_PARAMS_H */
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