FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_iosched.c

     /*
      * Copyright (c) 2008 The DragonFly Project.  All rights reserved.
      * 
      * This code is derived from software contributed to The DragonFly Project
      * by Matthew Dillon <dillon@backplane.com>
      * 
      * 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. Neither the name of The DragonFly Project 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 COPYRIGHT HOLDERS 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
     * COPYRIGHT HOLDERS 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.
     * 
     * $DragonFly: src/sys/kern/kern_iosched.c,v 1.1 2008/06/28 17:59:49 dillon Exp $
     */
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/kernel.h>
    #include <sys/proc.h>
    #include <sys/rtprio.h>
    #include <sys/queue.h>
    #include <machine/cpu.h>
    #include <sys/spinlock.h>
    #include <sys/iosched.h>
    #include <sys/sysctl.h>
    #include <sys/buf.h>
    #include <sys/limits.h>
    
    #include <sys/thread2.h>
    #include <sys/spinlock2.h>
    
    #include <vm/vm.h>
    #include <vm/vm_param.h>
    #include <vm/vm_kern.h>
    #include <vm/vm_extern.h>
    
    SYSCTL_NODE(, OID_AUTO, iosched, CTLFLAG_RW, 0, "I/O Scheduler");
    
    static int iosched_debug = 0;
    SYSCTL_INT(_iosched, OID_AUTO, debug, CTLFLAG_RW, &iosched_debug, 0, "");
    
    static struct iosched_data      ioscpu[SMP_MAXCPU];
    
    /*
     * MPSAFE
     */
    static int
    badjiosched(thread_t td, size_t bytes)
    {
            globaldata_t gd = mycpu;
            size_t iostotal;
            int factor;
            int i;
            int delta;
    
            iostotal = 0;
            for (i = 0; i < ncpus; ++i)
                    iostotal += ioscpu[i].iowbytes;
            if (SIZE_T_MAX / SMP_MAXCPU - td->td_iosdata.iowbytes < bytes)
                    bytes = SIZE_T_MAX / SMP_MAXCPU - td->td_iosdata.iowbytes;
            td->td_iosdata.iowbytes += bytes;
            ioscpu[gd->gd_cpuid].iowbytes += bytes;
            iostotal += bytes;
            delta = ticks - td->td_iosdata.lastticks;
            if (delta) {
                    td->td_iosdata.lastticks = ticks;
                    if (delta < 0 || delta > hz * 10)
                            delta = hz * 10;
                    /* be careful of interger overflows */
                    bytes = (int64_t)td->td_iosdata.iowbytes * delta / (hz * 10);
                    td->td_iosdata.iowbytes -= bytes;
                    ioscpu[gd->gd_cpuid].iowbytes -= bytes;
                    iostotal -= bytes;
            }
    
            /* be careful of interger overflows */
            if (iostotal > 0)
                    factor = (int64_t)td->td_iosdata.iowbytes * 100 / iostotal;
           else
                   factor = 50;
   
           if (delta && (iosched_debug & 1)) {
                   kprintf("proc %12s (%-5d) factor %3d (%zd/%zd)\n",
                           td->td_comm,
                           (td->td_lwp ? (int)td->td_lwp->lwp_proc->p_pid : -1),
                           factor, td->td_iosdata.iowbytes, iostotal);
           }
           return (factor);
   }
   
   void
   biosched_done(thread_t td)
   {
           globaldata_t gd = mycpu;
           size_t bytes;
   
           if ((bytes = td->td_iosdata.iowbytes) != 0) {
                   td->td_iosdata.iowbytes = 0;
                   ioscpu[gd->gd_cpuid].iowbytes -= bytes;
           }
   }
   
   /*
    * Caller intends to write (bytes)
    *
    * MPSAFE
    */
   void
   bwillwrite(int bytes)
   {
           long count;
           long factor;
   
           count = bd_heatup();
           if (count > 0) {
                   /* be careful of interger overflows */
                   factor = badjiosched(curthread, (size_t)bytes);
                   count = hidirtybufspace / 100 * factor;
                   bd_wait(count);
           }
   }
   
   /*
    * Caller intends to read (bytes)
    *
    * MPSAFE
    */
   void
   bwillread(int bytes)
   {
   }
   
   /*
    * Call intends to do an inode-modifying operation of some sort.
    *
    * MPSAFE
    */
   void
   bwillinode(int n)
   {
           long count;
           long factor;
   
           count = bd_heatup();
           if (count > 0) {
                   factor = badjiosched(curthread, PAGE_SIZE);
                   count = count * factor / 100;
                   bd_wait(count);
           }
   }
   

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