freebsd-skq/sys/i386/include/param.h
jhb 696704716d Implement preemption of kernel threads natively in the scheduler rather
than as one-off hacks in various other parts of the kernel:
- Add a function maybe_preempt() that is called from sched_add() to
  determine if a thread about to be added to a run queue should be
  preempted to directly.  If it is not safe to preempt or if the new
  thread does not have a high enough priority, then the function returns
  false and sched_add() adds the thread to the run queue.  If the thread
  should be preempted to but the current thread is in a nested critical
  section, then the flag TDF_OWEPREEMPT is set and the thread is added
  to the run queue.  Otherwise, mi_switch() is called immediately and the
  thread is never added to the run queue since it is switch to directly.
  When exiting an outermost critical section, if TDF_OWEPREEMPT is set,
  then clear it and call mi_switch() to perform the deferred preemption.
- Remove explicit preemption from ithread_schedule() as calling
  setrunqueue() now does all the correct work.  This also removes the
  do_switch argument from ithread_schedule().
- Do not use the manual preemption code in mtx_unlock if the architecture
  supports native preemption.
- Don't call mi_switch() in a loop during shutdown to give ithreads a
  chance to run if the architecture supports native preemption since
  the ithreads will just preempt DELAY().
- Don't call mi_switch() from the page zeroing idle thread for
  architectures that support native preemption as it is unnecessary.
- Native preemption is enabled on the same archs that supported ithread
  preemption, namely alpha, i386, and amd64.

This change should largely be a NOP for the default case as committed
except that we will do fewer context switches in a few cases and will
avoid the run queues completely when preempting.

Approved by:	scottl (with his re@ hat)
2004-07-02 20:21:44 +00:00

145 lines
4.3 KiB
C

/*-
* Copyright (c) 1990 The Regents of the University of California.
* All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* William Jolitz.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* from: @(#)param.h 5.8 (Berkeley) 6/28/91
* $FreeBSD$
*/
/*
* Machine dependent constants for Intel 386.
*/
/*
* Round p (pointer or byte index) up to a correctly-aligned value
* for all data types (int, long, ...). The result is unsigned int
* and must be cast to any desired pointer type.
*/
#ifndef _ALIGNBYTES
#define _ALIGNBYTES (sizeof(int) - 1)
#endif
#ifndef _ALIGN
#define _ALIGN(p) (((unsigned)(p) + _ALIGNBYTES) & ~_ALIGNBYTES)
#endif
#ifndef _MACHINE
#define _MACHINE i386
#endif
#ifndef _MACHINE_ARCH
#define _MACHINE_ARCH i386
#endif
#ifndef _NO_NAMESPACE_POLLUTION
#ifndef _MACHINE_PARAM_H_
#define _MACHINE_PARAM_H_
#ifndef MACHINE
#define MACHINE "i386"
#endif
#ifndef MACHINE_ARCH
#define MACHINE_ARCH "i386"
#endif
#define MID_MACHINE MID_I386
#ifdef SMP
#define MAXCPU 16
#else
#define MAXCPU 1
#endif /* SMP */
#define ALIGNBYTES _ALIGNBYTES
#define ALIGN(p) _ALIGN(p)
#define PAGE_SHIFT 12 /* LOG2(PAGE_SIZE) */
#define PAGE_SIZE (1<<PAGE_SHIFT) /* bytes/page */
#define PAGE_MASK (PAGE_SIZE-1)
#define NPTEPG (PAGE_SIZE/(sizeof (pt_entry_t)))
#ifdef PAE
#define NPGPTD 4
#define PDRSHIFT 21 /* LOG2(NBPDR) */
#else
#define NPGPTD 1
#define PDRSHIFT 22 /* LOG2(NBPDR) */
#endif
#define NBPTD (NPGPTD<<PAGE_SHIFT)
#define NPDEPTD (NBPTD/(sizeof (pd_entry_t)))
#define NPDEPG (PAGE_SIZE/(sizeof (pd_entry_t)))
#define NBPDR (1<<PDRSHIFT) /* bytes/page dir */
#define PDRMASK (NBPDR-1)
#define PREEMPTION
#define IOPAGES 2 /* pages of i/o permission bitmap */
#ifndef KSTACK_PAGES
#define KSTACK_PAGES 2 /* Includes pcb! */
#endif
#define KSTACK_GUARD_PAGES 1 /* pages of kstack guard; 0 disables */
#define UAREA_PAGES 1 /* holds struct user WITHOUT PCB (see def.) */
/*
* Ceiling on amount of swblock kva space, can be changed via
* the kern.maxswzone /boot/loader.conf variable.
*/
#ifndef VM_SWZONE_SIZE_MAX
#define VM_SWZONE_SIZE_MAX (32 * 1024 * 1024)
#endif
/*
* Ceiling on size of buffer cache (really only effects write queueing,
* the VM page cache is not effected), can be changed via
* the kern.maxbcache /boot/loader.conf variable.
*/
#ifndef VM_BCACHE_SIZE_MAX
#define VM_BCACHE_SIZE_MAX (200 * 1024 * 1024)
#endif
/*
* Mach derived conversion macros
*/
#define trunc_page(x) ((x) & ~PAGE_MASK)
#define round_page(x) (((x) + PAGE_MASK) & ~PAGE_MASK)
#define trunc_4mpage(x) ((x) & ~PDRMASK)
#define round_4mpage(x) ((((x)) + PDRMASK) & ~PDRMASK)
#define atop(x) ((x) >> PAGE_SHIFT)
#define ptoa(x) ((x) << PAGE_SHIFT)
#define i386_btop(x) ((x) >> PAGE_SHIFT)
#define i386_ptob(x) ((x) << PAGE_SHIFT)
#define pgtok(x) ((x) * (PAGE_SIZE / 1024))
#endif /* !_MACHINE_PARAM_H_ */
#endif /* !_NO_NAMESPACE_POLLUTION */