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

     /*-
      * SPDX-License-Identifier: BSD-3-Clause
      *
      * Copyright (c) 1980, 1986, 1989, 1993
      *      The Regents of the University of California.  All rights reserved.
      * (c) UNIX System Laboratories, Inc.
      * All or some portions of this file are derived from material licensed
      * to the University of California by American Telephone and Telegraph
      * Co. or Unix System Laboratories, Inc. and are reproduced herein with
     * the permission of UNIX System Laboratories, Inc.
     *
     * 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 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.
     *
     *      @(#)param.c     8.3 (Berkeley) 8/20/94
     */
    
    #include <sys/cdefs.h>
    __FBSDID("$FreeBSD$");
    
    #include "opt_param.h"
    #include "opt_msgbuf.h"
    #include "opt_maxphys.h"
    #include "opt_maxusers.h"
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/buf.h>
    #include <sys/kernel.h>
    #include <sys/limits.h>
    #include <sys/msgbuf.h>
    #include <sys/sysctl.h>
    #include <sys/proc.h>
    #include <sys/vnode.h>
    
    #include <vm/vm.h>
    #include <vm/vm_param.h>
    #include <vm/pmap.h>
    
    /*
     * System parameter formulae.
     */
    
    #ifndef HZ
    #  define       HZ 1000
    #  ifndef HZ_VM
    #    define     HZ_VM 100
    #  endif
    #else
    #  ifndef HZ_VM
    #    define     HZ_VM HZ
    #  endif
    #endif
    #define NPROC (20 + 16 * maxusers)
    #ifndef NBUF
    #define NBUF 0
    #endif
    #ifndef MAXFILES
    #define MAXFILES (40 + 32 * maxusers)
    #endif
    
    static int sysctl_kern_vm_guest(SYSCTL_HANDLER_ARGS);
    
    int     hz;                             /* system clock's frequency */
    int     tick;                           /* usec per tick (1000000 / hz) */
    time_t  tick_seconds_max;               /* max hz * seconds an integer can hold */
    struct bintime tick_bt;                 /* bintime per tick (1s / hz) */
    sbintime_t tick_sbt;
    int     maxusers;                       /* base tunable */
    int     maxproc;                        /* maximum # of processes */
    int     maxprocperuid;                  /* max # of procs per user */
    int     maxfiles;                       /* sys. wide open files limit */
    int     maxfilesperproc;                /* per-proc open files limit */
    int     msgbufsize;                     /* size of kernel message buffer */
    int     nbuf;                           /* number of bcache bufs */
    int     bio_transient_maxcnt;
    int     ngroups_max;                    /* max # groups per process */
    int     nswbuf;
   pid_t   pid_max = PID_MAX;
   u_long  maxswzone;                      /* max swmeta KVA storage */
   u_long  maxbcache;                      /* max buffer cache KVA storage */
   u_long  maxpipekva;                     /* Limit on pipe KVA */
   u_long  maxphys;                        /* max raw I/O transfer size */
   int     vm_guest = VM_GUEST_NO;         /* Running as virtual machine guest? */
   u_long  maxtsiz;                        /* max text size */
   u_long  dfldsiz;                        /* initial data size limit */
   u_long  maxdsiz;                        /* max data size */
   u_long  dflssiz;                        /* initial stack size limit */
   u_long  maxssiz;                        /* max stack size */
   u_long  sgrowsiz;                       /* amount to grow stack */
   
   SYSCTL_INT(_kern, OID_AUTO, hz, CTLFLAG_RDTUN | CTLFLAG_NOFETCH, &hz, 0,
       "Number of clock ticks per second");
   SYSCTL_INT(_kern, OID_AUTO, hz_max, CTLFLAG_RD, SYSCTL_NULL_INT_PTR, HZ_MAXIMUM,
       "Maximum hz value supported");
   SYSCTL_INT(_kern, OID_AUTO, hz_min, CTLFLAG_RD, SYSCTL_NULL_INT_PTR, HZ_MINIMUM,
       "Minimum hz value supported");
   SYSCTL_INT(_kern, OID_AUTO, nbuf, CTLFLAG_RDTUN | CTLFLAG_NOFETCH, &nbuf, 0,
       "Number of buffers in the buffer cache");
   SYSCTL_INT(_kern, OID_AUTO, nswbuf, CTLFLAG_RDTUN | CTLFLAG_NOFETCH, &nswbuf, 0,
       "Number of swap buffers");
   SYSCTL_INT(_kern, OID_AUTO, msgbufsize, CTLFLAG_RDTUN | CTLFLAG_NOFETCH, &msgbufsize, 0,
       "Size of the kernel message buffer");
   SYSCTL_LONG(_kern, OID_AUTO, maxswzone, CTLFLAG_RDTUN | CTLFLAG_NOFETCH, &maxswzone, 0,
       "Maximum memory for swap metadata");
   SYSCTL_LONG(_kern, OID_AUTO, maxbcache, CTLFLAG_RDTUN | CTLFLAG_NOFETCH, &maxbcache, 0,
       "Maximum value of vfs.maxbufspace");
   SYSCTL_INT(_kern, OID_AUTO, bio_transient_maxcnt, CTLFLAG_RDTUN | CTLFLAG_NOFETCH,
       &bio_transient_maxcnt, 0,
       "Maximum number of transient BIOs mappings");
   SYSCTL_ULONG(_kern, OID_AUTO, maxtsiz, CTLFLAG_RWTUN | CTLFLAG_NOFETCH, &maxtsiz, 0,
       "Maximum text size");
   SYSCTL_ULONG(_kern, OID_AUTO, dfldsiz, CTLFLAG_RWTUN | CTLFLAG_NOFETCH, &dfldsiz, 0,
       "Initial data size limit");
   SYSCTL_ULONG(_kern, OID_AUTO, maxdsiz, CTLFLAG_RWTUN | CTLFLAG_NOFETCH, &maxdsiz, 0,
       "Maximum data size");
   SYSCTL_ULONG(_kern, OID_AUTO, dflssiz, CTLFLAG_RWTUN | CTLFLAG_NOFETCH, &dflssiz, 0,
       "Initial stack size limit");
   SYSCTL_ULONG(_kern, OID_AUTO, maxssiz, CTLFLAG_RWTUN | CTLFLAG_NOFETCH, &maxssiz, 0,
       "Maximum stack size");
   SYSCTL_ULONG(_kern, OID_AUTO, sgrowsiz, CTLFLAG_RWTUN | CTLFLAG_NOFETCH, &sgrowsiz, 0,
       "Amount to grow stack on a stack fault");
   SYSCTL_PROC(_kern, OID_AUTO, vm_guest,
       CTLFLAG_RD | CTLTYPE_STRING | CTLFLAG_MPSAFE, NULL, 0,
       sysctl_kern_vm_guest, "A",
       "Virtual machine guest detected?");
   
   /*
    * The elements of this array are ordered based upon the values of the
    * corresponding enum VM_GUEST members.
    */
   static const char *const vm_guest_sysctl_names[] = {
           [VM_GUEST_NO] = "none",
           [VM_GUEST_VM] = "generic",
           [VM_GUEST_XEN] = "xen",
           [VM_GUEST_HV] = "hv",
           [VM_GUEST_VMWARE] = "vmware",
           [VM_GUEST_KVM] = "kvm",
           [VM_GUEST_BHYVE] = "bhyve",
           [VM_GUEST_VBOX] = "vbox",
           [VM_GUEST_PARALLELS] = "parallels",
           [VM_LAST] = NULL
   };
   CTASSERT(nitems(vm_guest_sysctl_names) - 1 == VM_LAST);
   
   /*
    * Boot time overrides that are not scaled against main memory
    */
   void
   init_param1(void)
   {
   
   #if !defined(__mips__) && !defined(__arm64__)
           TUNABLE_INT_FETCH("kern.kstack_pages", &kstack_pages);
   #endif
           hz = -1;
           TUNABLE_INT_FETCH("kern.hz", &hz);
           if (hz == -1)
                   hz = vm_guest > VM_GUEST_NO ? HZ_VM : HZ;
   
           /* range check the "hz" value */
           if (__predict_false(hz < HZ_MINIMUM))
                   hz = HZ_MINIMUM;
           else if (__predict_false(hz > HZ_MAXIMUM))
                   hz = HZ_MAXIMUM;
   
           tick = 1000000 / hz;
           tick_sbt = SBT_1S / hz;
           tick_bt = sbttobt(tick_sbt);
           tick_seconds_max = INT_MAX / hz;
   
           /*
            * Arrange for ticks to wrap 10 minutes after boot to help catch
            * sign problems sooner.
            */
           ticks = INT_MAX - (hz * 10 * 60);
   
           vn_lock_pair_pause_max = hz / 100;
           if (vn_lock_pair_pause_max == 0)
                   vn_lock_pair_pause_max = 1;
   
   #ifdef VM_SWZONE_SIZE_MAX
           maxswzone = VM_SWZONE_SIZE_MAX;
   #endif
           TUNABLE_LONG_FETCH("kern.maxswzone", &maxswzone);
   #ifdef VM_BCACHE_SIZE_MAX
           maxbcache = VM_BCACHE_SIZE_MAX;
   #endif
           TUNABLE_LONG_FETCH("kern.maxbcache", &maxbcache);
           msgbufsize = MSGBUF_SIZE;
           TUNABLE_INT_FETCH("kern.msgbufsize", &msgbufsize);
   
           maxtsiz = MAXTSIZ;
           TUNABLE_ULONG_FETCH("kern.maxtsiz", &maxtsiz);
           dfldsiz = DFLDSIZ;
           TUNABLE_ULONG_FETCH("kern.dfldsiz", &dfldsiz);
           maxdsiz = MAXDSIZ;
           TUNABLE_ULONG_FETCH("kern.maxdsiz", &maxdsiz);
           dflssiz = DFLSSIZ;
           TUNABLE_ULONG_FETCH("kern.dflssiz", &dflssiz);
           maxssiz = MAXSSIZ;
           TUNABLE_ULONG_FETCH("kern.maxssiz", &maxssiz);
           sgrowsiz = SGROWSIZ;
           TUNABLE_ULONG_FETCH("kern.sgrowsiz", &sgrowsiz);
   
           /*
            * Let the administrator set {NGROUPS_MAX}, but disallow values
            * less than NGROUPS_MAX which would violate POSIX.1-2008 or
            * greater than INT_MAX-1 which would result in overflow.
            */
           ngroups_max = NGROUPS_MAX;
           TUNABLE_INT_FETCH("kern.ngroups", &ngroups_max);
           if (ngroups_max < NGROUPS_MAX)
                   ngroups_max = NGROUPS_MAX;
   
           /*
            * Only allow to lower the maximal pid.
            * Prevent setting up a non-bootable system if pid_max is too low.
            */
           TUNABLE_INT_FETCH("kern.pid_max", &pid_max);
           if (pid_max > PID_MAX)
                   pid_max = PID_MAX;
           else if (pid_max < 300)
                   pid_max = 300;
   
           TUNABLE_INT_FETCH("vfs.unmapped_buf_allowed", &unmapped_buf_allowed);
   }
   
   /*
    * Boot time overrides that are scaled against main memory
    */
   void
   init_param2(long physpages)
   {
   
           /* Base parameters */
           maxusers = MAXUSERS;
           TUNABLE_INT_FETCH("kern.maxusers", &maxusers);
           if (maxusers == 0) {
                   maxusers = physpages / (2 * 1024 * 1024 / PAGE_SIZE);
                   if (maxusers < 32)
                           maxusers = 32;
   #ifdef VM_MAX_AUTOTUNE_MAXUSERS
                   if (maxusers > VM_MAX_AUTOTUNE_MAXUSERS)
                           maxusers = VM_MAX_AUTOTUNE_MAXUSERS;
   #endif
                   /*
                    * Scales down the function in which maxusers grows once
                    * we hit 384.
                    */
                   if (maxusers > 384)
                           maxusers = 384 + ((maxusers - 384) / 8);
           }
   
           /*
            * The following can be overridden after boot via sysctl.  Note:
            * unless overridden, these macros are ultimately based on maxusers.
            * Limit maxproc so that kmap entries cannot be exhausted by
            * processes.
            */
           maxproc = NPROC;
           TUNABLE_INT_FETCH("kern.maxproc", &maxproc);
           if (maxproc > (physpages / 12))
                   maxproc = physpages / 12;
           if (maxproc > pid_max)
                   maxproc = pid_max;
           maxprocperuid = (maxproc * 9) / 10;
   
           /*
            * The default limit for maxfiles is 1/12 of the number of
            * physical page but not less than 16 times maxusers.
            * At most it can be 1/6 the number of physical pages.
            */
           maxfiles = imax(MAXFILES, physpages / 8);
           TUNABLE_INT_FETCH("kern.maxfiles", &maxfiles);
           if (maxfiles > (physpages / 4))
                   maxfiles = physpages / 4;
           maxfilesperproc = (maxfiles / 10) * 9;
           TUNABLE_INT_FETCH("kern.maxfilesperproc", &maxfilesperproc);
   
           /*
            * Cannot be changed after boot.
            */
           nbuf = NBUF;
           TUNABLE_INT_FETCH("kern.nbuf", &nbuf);
           TUNABLE_INT_FETCH("kern.bio_transient_maxcnt", &bio_transient_maxcnt);
           maxphys = MAXPHYS;
           TUNABLE_ULONG_FETCH("kern.maxphys", &maxphys);
           if (maxphys == 0) {
                   maxphys = MAXPHYS;
           } else if (__bitcountl(maxphys) != 1) { /* power of two */
                   if (flsl(maxphys) == NBBY * sizeof(maxphys))
                           maxphys = MAXPHYS;
                   else
                           maxphys = 1UL << flsl(maxphys);
           }
           if (maxphys < PAGE_SIZE)
                   maxphys = MAXPHYS;
   
           /*
            * Physical buffers are pre-allocated buffers (struct buf) that
            * are used as temporary holders for I/O, such as paging I/O.
            */
           TUNABLE_INT_FETCH("kern.nswbuf", &nswbuf);
   
           /*
            * The default for maxpipekva is min(1/64 of the kernel address space,
            * max(1/64 of main memory, 512KB)).  See sys_pipe.c for more details.
            */
           maxpipekva = ptoa(physpages / 64);
           TUNABLE_LONG_FETCH("kern.ipc.maxpipekva", &maxpipekva);
           if (maxpipekva < 512 * 1024)
                   maxpipekva = 512 * 1024;
           if (maxpipekva > (VM_MAX_KERNEL_ADDRESS - VM_MIN_KERNEL_ADDRESS) / 64)
                   maxpipekva = (VM_MAX_KERNEL_ADDRESS - VM_MIN_KERNEL_ADDRESS) /
                       64;
   }
   
   /*
    * Sysctl stringifying handler for kern.vm_guest.
    */
   static int
   sysctl_kern_vm_guest(SYSCTL_HANDLER_ARGS)
   {
           return (SYSCTL_OUT_STR(req, vm_guest_sysctl_names[vm_guest]));
   }

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