FreeBSD/Linux Kernel Cross Reference
sys/vm/vm_page2.h

     /*-
      * Copyright (c) 1982, 1986, 1993
      *      The Regents of the University of California.  All rights reserved.
      *
      * 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.
     * 3. All advertising materials mentioning features or use of this software
     *    must display the following acknowledgement:
     *      This product includes software developed by the University of
     *      California, Berkeley and its contributors.
     * 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
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     * 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.
     *
     *      @(#)vmmeter.h   8.2 (Berkeley) 7/10/94
     * $FreeBSD: src/sys/sys/vmmeter.h,v 1.21.2.2 2002/10/10 19:28:21 dillon Exp $
     */
    
    #ifndef _VM_VM_PAGE2_H_
    #define _VM_VM_PAGE2_H_
    
    #ifndef _SYS_VMMETER_H_
    #include <sys/vmmeter.h>
    #endif
    #ifndef _SYS_QUEUE_H_
    #include <sys/queue.h>
    #endif
    #ifndef _VM_VM_PAGE_H_
    #include <vm/vm_page.h>
    #endif
    #ifndef _SYS_SPINLOCK_H_
    #include <sys/spinlock.h>
    #endif
    #ifndef _SYS_SPINLOCK2_H_
    #include <sys/spinlock2.h>
    #endif
    
    #ifdef _KERNEL
    
    /*
     * Return TRUE if we are under our severe low-free-pages threshold
     *
     * This causes user processes to stall to avoid exhausting memory that
     * the kernel might need.
     *
     * reserved < severe < minimum < target < paging_target
     */
    static __inline 
    int
    vm_page_count_severe(void)
    {
        return (vmstats.v_free_severe >
                vmstats.v_free_count + vmstats.v_cache_count ||
                vmstats.v_free_reserved > vmstats.v_free_count);
    }
    
    /*
     * Return TRUE if we are under our minimum low-free-pages threshold.
     * This activates the pageout demon.  The pageout demon tries to
     * reach the target but may stop once it satisfies the minimum.
     *
     * reserved < severe < minimum < target < paging_target
     */
    static __inline 
    int
    vm_page_count_min(int donotcount)
    {
        return (vmstats.v_free_min + donotcount >
                (vmstats.v_free_count + vmstats.v_cache_count) ||
                vmstats.v_free_reserved > vmstats.v_free_count);
    }
    
    /*
     * Return TRUE if we are under our free page target.  The pageout demon
     * tries to reach the target but may stop once it gets past the min.
     *
     * User threads doing normal allocations might wait based on this
     * function but MUST NOT wait in a loop based on this function as the
     * VM load may prevent the target from being reached.
     */
    static __inline 
   int
   vm_page_count_target(void)
   {
       return (vmstats.v_free_target >
               (vmstats.v_free_count + vmstats.v_cache_count) ||
               vmstats.v_free_reserved > vmstats.v_free_count);
   }
   
   /*
    * Return the number of pages the pageout daemon needs to move into the
    * cache or free lists.  A negative number means we have sufficient free
    * pages.
    *
    * The target free+cache is greater than vm_page_count_target().  The
    * frontend uses vm_page_count_target() while the backend continue freeing
    * based on vm_paging_target().
    *
    * This function DOES NOT return TRUE or FALSE.
    */
   static __inline 
   int
   vm_paging_target(void)
   {
       return (
           (vmstats.v_free_target + vmstats.v_cache_min) - 
           (vmstats.v_free_count + vmstats.v_cache_count)
       );
   }
   
   /*
    * Return TRUE if hysteresis dictates we should nominally wakeup the
    * pageout daemon to start working on freeing up some memory.  This
    * routine should NOT be used to determine when to block on the VM system.
    * We want to wakeup the pageout daemon before we might otherwise block.
    *
    * Paging begins when cache+free drops below cache_min + free_min.
    */
   static __inline 
   int
   vm_paging_needed(void)
   {
       if (vmstats.v_free_min + vmstats.v_cache_min >
           vmstats.v_free_count + vmstats.v_cache_count) {
                   return 1;
       }
       if (vmstats.v_free_min > vmstats.v_free_count)
                   return 1;
       return 0;
   }
   
   static __inline
   void
   vm_page_event(vm_page_t m, vm_page_event_t event)
   {
       if (m->flags & PG_ACTIONLIST)
           vm_page_event_internal(m, event);
   }
   
   static __inline
   void
   vm_page_init_action(vm_page_t m, vm_page_action_t action,
                       void (*func)(vm_page_t, vm_page_action_t), void *data)
   {
       action->m = m;
       action->func = func;
       action->data = data;
   }
   
   /*
    * Clear dirty bits in the VM page but truncate the
    * end to a DEV_BSIZE'd boundary.
    *
    * Used when reading data in, typically via getpages.
    * The partial device block at the end of the truncation
    * range should not lose its dirty bit.
    *
    * NOTE: This function does not clear the pmap modified bit.
    */
   static __inline
   void
   vm_page_clear_dirty_end_nonincl(vm_page_t m, int base, int size)
   {
       size = (base + size) & ~DEV_BMASK;
       if (base < size)
           vm_page_clear_dirty(m, base, size - base);
   }
   
   /*
    * Clear dirty bits in the VM page but truncate the
    * beginning to a DEV_BSIZE'd boundary.
    *
    * Used when truncating a buffer.  The partial device
    * block at the beginning of the truncation range
    * should not lose its dirty bit.
    *
    * NOTE: This function does not clear the pmap modified bit.
    */
   static __inline
   void
   vm_page_clear_dirty_beg_nonincl(vm_page_t m, int base, int size)
   {
       size += base;
       base = (base + DEV_BMASK) & ~DEV_BMASK;
       if (base < size)
           vm_page_clear_dirty(m, base, size - base);
   }
   
   static __inline
   void
   vm_page_spin_lock(vm_page_t m)
   {
       spin_pool_lock(m);
   }
   
   static __inline
   void
   vm_page_spin_unlock(vm_page_t m)
   {
       spin_pool_unlock(m);
   }
   
   /*
    * Wire a vm_page that is already wired.  Does not require a busied
    * page.
    */
   static __inline
   void
   vm_page_wire_quick(vm_page_t m)
   {
       if (atomic_fetchadd_int(&m->wire_count, 1) == 0)
           panic("vm_page_wire_quick: wire_count was 0");
   }
   
   /*
    * Unwire a vm_page quickly, does not require a busied page.
    *
    * This routine refuses to drop the wire_count to 0 and will return
    * TRUE if it would have had to (instead of decrementing it to 0).
    * The caller can then busy the page and deal with it.
    */
   static __inline
   int
   vm_page_unwire_quick(vm_page_t m)
   {
       KKASSERT(m->wire_count > 0);
       for (;;) {
           u_int wire_count = m->wire_count;
   
           cpu_ccfence();
           if (wire_count == 1)
                   return TRUE;
           if (atomic_cmpset_int(&m->wire_count, wire_count, wire_count - 1))
                   return FALSE;
       }
   }
   
   /*
    *      Functions implemented as macros
    */
   
   static __inline void
   vm_page_flag_set(vm_page_t m, unsigned int bits)
   {
           atomic_set_int(&(m)->flags, bits);
   }
   
   static __inline void
   vm_page_flag_clear(vm_page_t m, unsigned int bits)
   {
           atomic_clear_int(&(m)->flags, bits);
   }
   
   /*
    * Wakeup anyone waiting for the page after potentially unbusying
    * (hard or soft) or doing other work on a page that might make a
    * waiter ready.  The setting of PG_WANTED is integrated into the
    * related flags and it can't be set once the flags are already
    * clear, so there should be no races here.
    */
   
   static __inline void
   vm_page_flash(vm_page_t m)
   {
           if (m->flags & PG_WANTED) {
                   vm_page_flag_clear(m, PG_WANTED);
                   wakeup(m);
           }
   }
   
   /*
    * Reduce the protection of a page.  This routine never raises the
    * protection and therefore can be safely called if the page is already
    * at VM_PROT_NONE (it will be a NOP effectively ).
    *
    * VM_PROT_NONE will remove all user mappings of a page.  This is often
    * necessary when a page changes state (for example, turns into a copy-on-write
    * page or needs to be frozen for write I/O) in order to force a fault, or
    * to force a page's dirty bits to be synchronized and avoid hardware
    * (modified/accessed) bit update races with pmap changes.
    *
    * Since 'prot' is usually a constant, this inline usually winds up optimizing
    * out the primary conditional.
    *
    * WARNING: VM_PROT_NONE can block, but will loop until all mappings have
    * been cleared.  Callers should be aware that other page related elements
    * might have changed, however.
    */
   static __inline void
   vm_page_protect(vm_page_t m, int prot)
   {
           KKASSERT(m->flags & PG_BUSY);
           if (prot == VM_PROT_NONE) {
                   if (m->flags & (PG_WRITEABLE|PG_MAPPED)) {
                           pmap_page_protect(m, VM_PROT_NONE);
                           /* PG_WRITEABLE & PG_MAPPED cleared by call */
                   }
           } else if ((prot == VM_PROT_READ) && (m->flags & PG_WRITEABLE)) {
                   pmap_page_protect(m, VM_PROT_READ);
                   /* PG_WRITEABLE cleared by call */
           }
   }
   
   /*
    * Zero-fill the specified page.  The entire contents of the page will be
    * zero'd out.
    */
   static __inline boolean_t
   vm_page_zero_fill(vm_page_t m)
   {
           pmap_zero_page(VM_PAGE_TO_PHYS(m));
           return (TRUE);
   }
   
   /*
    * Copy the contents of src_m to dest_m.  The pages must be stable but spl
    * and other protections depend on context.
    */
   static __inline void
   vm_page_copy(vm_page_t src_m, vm_page_t dest_m)
   {
           pmap_copy_page(VM_PAGE_TO_PHYS(src_m), VM_PAGE_TO_PHYS(dest_m));
           dest_m->valid = VM_PAGE_BITS_ALL;
           dest_m->dirty = VM_PAGE_BITS_ALL;
   }
   
   /*
    * Free a page.  The page must be marked BUSY.
    *
    * Always clear PG_ZERO when freeing a page, which ensures the flag is not
    * set unless we are absolutely certain the page is zerod.  This is
    * particularly important when the vm_page_alloc*() code moves pages from
    * PQ_CACHE to PQ_FREE.
    */
   static __inline void
   vm_page_free(vm_page_t m)
   {
           vm_page_flag_clear(m, PG_ZERO);
           vm_page_free_toq(m);
   }
   
   /*
    * Free a page to the zerod-pages queue.  The caller must ensure that the
    * page has been zerod.
    */
   static __inline void
   vm_page_free_zero(vm_page_t m)
   {
   #ifdef PMAP_DEBUG
   #ifdef PHYS_TO_DMAP
           char *p = (char *)PHYS_TO_DMAP(VM_PAGE_TO_PHYS(m));
           int i;
   
           for (i = 0; i < PAGE_SIZE; i++) {
                   if (p[i] != 0) {
                           panic("non-zero page in vm_page_free_zero()");
                   }
           }
   #endif
   #endif
           vm_page_flag_set(m, PG_ZERO);
           vm_page_free_toq(m);
   }
   
   /*
    * Set page to not be dirty.  Note: does not clear pmap modify bits .
    */
   static __inline void
   vm_page_undirty(vm_page_t m)
   {
           m->dirty = 0;
   }
   
   #endif  /* _KERNEL */
   #endif  /* _VM_VM_PAGE2_H_ */
   

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