The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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

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    1 /*-
    2  * Copyright (c) 1980, 1986, 1989, 1993
    3  *      The Regents of the University of California.  All rights reserved.
    4  * (c) UNIX System Laboratories, Inc.
    5  * All or some portions of this file are derived from material licensed
    6  * to the University of California by American Telephone and Telegraph
    7  * Co. or Unix System Laboratories, Inc. and are reproduced herein with
    8  * the permission of UNIX System Laboratories, Inc.
    9  *
   10  * Redistribution and use in source and binary forms, with or without
   11  * modification, are permitted provided that the following conditions
   12  * are met:
   13  * 1. Redistributions of source code must retain the above copyright
   14  *    notice, this list of conditions and the following disclaimer.
   15  * 2. Redistributions in binary form must reproduce the above copyright
   16  *    notice, this list of conditions and the following disclaimer in the
   17  *    documentation and/or other materials provided with the distribution.
   18  * 4. Neither the name of the University nor the names of its contributors
   19  *    may be used to endorse or promote products derived from this software
   20  *    without specific prior written permission.
   21  *
   22  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   23  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   24  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   25  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   26  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   27  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   28  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   29  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   30  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   31  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   32  * SUCH DAMAGE.
   33  *
   34  *      @(#)param.c     8.3 (Berkeley) 8/20/94
   35  */
   36 
   37 #include <sys/cdefs.h>
   38 __FBSDID("$FreeBSD: stable/10/sys/kern/subr_param.c 288690 2015-10-05 05:33:30Z kib $");
   39 
   40 #include "opt_param.h"
   41 #include "opt_msgbuf.h"
   42 #include "opt_maxusers.h"
   43 
   44 #include <sys/param.h>
   45 #include <sys/systm.h>
   46 #include <sys/kernel.h>
   47 #include <sys/limits.h>
   48 #include <sys/msgbuf.h>
   49 #include <sys/sysctl.h>
   50 #include <sys/proc.h>
   51 
   52 #include <vm/vm.h>
   53 #include <vm/vm_param.h>
   54 #include <vm/pmap.h>
   55 
   56 /*
   57  * System parameter formulae.
   58  */
   59 
   60 #ifndef HZ
   61 #  if defined(__mips__) || defined(__arm__)
   62 #    define     HZ 100
   63 #  else
   64 #    define     HZ 1000
   65 #  endif
   66 #  ifndef HZ_VM
   67 #    define     HZ_VM 100
   68 #  endif
   69 #else
   70 #  ifndef HZ_VM
   71 #    define     HZ_VM HZ
   72 #  endif
   73 #endif
   74 #define NPROC (20 + 16 * maxusers)
   75 #ifndef NBUF
   76 #define NBUF 0
   77 #endif
   78 #ifndef MAXFILES
   79 #define MAXFILES (40 + 32 * maxusers)
   80 #endif
   81 
   82 static int sysctl_kern_vm_guest(SYSCTL_HANDLER_ARGS);
   83 
   84 int     hz;                             /* system clock's frequency */
   85 int     tick;                           /* usec per tick (1000000 / hz) */
   86 struct bintime tick_bt;                 /* bintime per tick (1s / hz) */
   87 sbintime_t tick_sbt;
   88 int     maxusers;                       /* base tunable */
   89 int     maxproc;                        /* maximum # of processes */
   90 int     maxprocperuid;                  /* max # of procs per user */
   91 int     maxfiles;                       /* sys. wide open files limit */
   92 int     maxfilesperproc;                /* per-proc open files limit */
   93 int     msgbufsize;                     /* size of kernel message buffer */
   94 int     nbuf;
   95 int     bio_transient_maxcnt;
   96 int     ngroups_max;                    /* max # groups per process */
   97 int     nswbuf;
   98 pid_t   pid_max = PID_MAX;
   99 long    maxswzone;                      /* max swmeta KVA storage */
  100 long    maxbcache;                      /* max buffer cache KVA storage */
  101 long    maxpipekva;                     /* Limit on pipe KVA */
  102 #ifdef XEN
  103 int     vm_guest = VM_GUEST_XEN;
  104 #else
  105 int     vm_guest = VM_GUEST_NO;         /* Running as virtual machine guest? */
  106 #endif
  107 u_long  maxtsiz;                        /* max text size */
  108 u_long  dfldsiz;                        /* initial data size limit */
  109 u_long  maxdsiz;                        /* max data size */
  110 u_long  dflssiz;                        /* initial stack size limit */
  111 u_long  maxssiz;                        /* max stack size */
  112 u_long  sgrowsiz;                       /* amount to grow stack */
  113 
  114 SYSCTL_INT(_kern, OID_AUTO, hz, CTLFLAG_RDTUN, &hz, 0,
  115     "Number of clock ticks per second");
  116 SYSCTL_INT(_kern, OID_AUTO, nbuf, CTLFLAG_RDTUN, &nbuf, 0,
  117     "Number of buffers in the buffer cache");
  118 SYSCTL_INT(_kern, OID_AUTO, nswbuf, CTLFLAG_RDTUN, &nswbuf, 0,
  119     "Number of swap buffers");
  120 SYSCTL_INT(_kern, OID_AUTO, msgbufsize, CTLFLAG_RDTUN, &msgbufsize, 0,
  121     "Size of the kernel message buffer");
  122 SYSCTL_LONG(_kern, OID_AUTO, maxswzone, CTLFLAG_RDTUN, &maxswzone, 0,
  123     "Maximum memory for swap metadata");
  124 SYSCTL_LONG(_kern, OID_AUTO, maxbcache, CTLFLAG_RDTUN, &maxbcache, 0,
  125     "Maximum value of vfs.maxbufspace");
  126 SYSCTL_INT(_kern, OID_AUTO, bio_transient_maxcnt, CTLFLAG_RDTUN,
  127     &bio_transient_maxcnt, 0,
  128     "Maximum number of transient BIOs mappings");
  129 SYSCTL_ULONG(_kern, OID_AUTO, maxtsiz, CTLFLAG_RW | CTLFLAG_TUN, &maxtsiz, 0,
  130     "Maximum text size");
  131 SYSCTL_ULONG(_kern, OID_AUTO, dfldsiz, CTLFLAG_RW | CTLFLAG_TUN, &dfldsiz, 0,
  132     "Initial data size limit");
  133 SYSCTL_ULONG(_kern, OID_AUTO, maxdsiz, CTLFLAG_RW | CTLFLAG_TUN, &maxdsiz, 0,
  134     "Maximum data size");
  135 SYSCTL_ULONG(_kern, OID_AUTO, dflssiz, CTLFLAG_RW | CTLFLAG_TUN, &dflssiz, 0,
  136     "Initial stack size limit");
  137 SYSCTL_ULONG(_kern, OID_AUTO, maxssiz, CTLFLAG_RW | CTLFLAG_TUN, &maxssiz, 0,
  138     "Maximum stack size");
  139 SYSCTL_ULONG(_kern, OID_AUTO, sgrowsiz, CTLFLAG_RW | CTLFLAG_TUN, &sgrowsiz, 0,
  140     "Amount to grow stack on a stack fault");
  141 SYSCTL_PROC(_kern, OID_AUTO, vm_guest, CTLFLAG_RD | CTLTYPE_STRING,
  142     NULL, 0, sysctl_kern_vm_guest, "A",
  143     "Virtual machine guest detected?");
  144 
  145 /*
  146  * These have to be allocated somewhere; allocating
  147  * them here forces loader errors if this file is omitted
  148  * (if they've been externed everywhere else; hah!).
  149  */
  150 struct  buf *swbuf;
  151 
  152 /*
  153  * The elements of this array are ordered based upon the values of the
  154  * corresponding enum VM_GUEST members.
  155  */
  156 static const char *const vm_guest_sysctl_names[] = {
  157         "none",
  158         "generic",
  159         "xen",
  160         "hv",
  161         "vmware",
  162         NULL
  163 };
  164 CTASSERT(nitems(vm_guest_sysctl_names) - 1 == VM_LAST);
  165 
  166 /*
  167  * Boot time overrides that are not scaled against main memory
  168  */
  169 void
  170 init_param1(void)
  171 {
  172 
  173         hz = -1;
  174         TUNABLE_INT_FETCH("kern.hz", &hz);
  175         if (hz == -1)
  176                 hz = vm_guest > VM_GUEST_NO ? HZ_VM : HZ;
  177         tick = 1000000 / hz;
  178         tick_sbt = SBT_1S / hz;
  179         tick_bt = sbttobt(tick_sbt);
  180 
  181 #ifdef VM_SWZONE_SIZE_MAX
  182         maxswzone = VM_SWZONE_SIZE_MAX;
  183 #endif
  184         TUNABLE_LONG_FETCH("kern.maxswzone", &maxswzone);
  185 #ifdef VM_BCACHE_SIZE_MAX
  186         maxbcache = VM_BCACHE_SIZE_MAX;
  187 #endif
  188         TUNABLE_LONG_FETCH("kern.maxbcache", &maxbcache);
  189         msgbufsize = MSGBUF_SIZE;
  190         TUNABLE_INT_FETCH("kern.msgbufsize", &msgbufsize);
  191 
  192         maxtsiz = MAXTSIZ;
  193         TUNABLE_ULONG_FETCH("kern.maxtsiz", &maxtsiz);
  194         dfldsiz = DFLDSIZ;
  195         TUNABLE_ULONG_FETCH("kern.dfldsiz", &dfldsiz);
  196         maxdsiz = MAXDSIZ;
  197         TUNABLE_ULONG_FETCH("kern.maxdsiz", &maxdsiz);
  198         dflssiz = DFLSSIZ;
  199         TUNABLE_ULONG_FETCH("kern.dflssiz", &dflssiz);
  200         maxssiz = MAXSSIZ;
  201         TUNABLE_ULONG_FETCH("kern.maxssiz", &maxssiz);
  202         sgrowsiz = SGROWSIZ;
  203         TUNABLE_ULONG_FETCH("kern.sgrowsiz", &sgrowsiz);
  204 
  205         /*
  206          * Let the administrator set {NGROUPS_MAX}, but disallow values
  207          * less than NGROUPS_MAX which would violate POSIX.1-2008 or
  208          * greater than INT_MAX-1 which would result in overflow.
  209          */
  210         ngroups_max = NGROUPS_MAX;
  211         TUNABLE_INT_FETCH("kern.ngroups", &ngroups_max);
  212         if (ngroups_max < NGROUPS_MAX)
  213                 ngroups_max = NGROUPS_MAX;
  214 
  215         /*
  216          * Only allow to lower the maximal pid.
  217          * Prevent setting up a non-bootable system if pid_max is too low.
  218          */
  219         TUNABLE_INT_FETCH("kern.pid_max", &pid_max);
  220         if (pid_max > PID_MAX)
  221                 pid_max = PID_MAX;
  222         else if (pid_max < 300)
  223                 pid_max = 300;
  224 
  225         TUNABLE_INT_FETCH("vfs.unmapped_buf_allowed", &unmapped_buf_allowed);
  226 }
  227 
  228 /*
  229  * Boot time overrides that are scaled against main memory
  230  */
  231 void
  232 init_param2(long physpages)
  233 {
  234 
  235         /* Base parameters */
  236         maxusers = MAXUSERS;
  237         TUNABLE_INT_FETCH("kern.maxusers", &maxusers);
  238         if (maxusers == 0) {
  239                 maxusers = physpages / (2 * 1024 * 1024 / PAGE_SIZE);
  240                 if (maxusers < 32)
  241                         maxusers = 32;
  242 #ifdef VM_MAX_AUTOTUNE_MAXUSERS
  243                 if (maxusers > VM_MAX_AUTOTUNE_MAXUSERS)
  244                         maxusers = VM_MAX_AUTOTUNE_MAXUSERS;
  245 #endif
  246                 /*
  247                  * Scales down the function in which maxusers grows once
  248                  * we hit 384.
  249                  */
  250                 if (maxusers > 384)
  251                         maxusers = 384 + ((maxusers - 384) / 8);
  252         }
  253 
  254         /*
  255          * The following can be overridden after boot via sysctl.  Note:
  256          * unless overriden, these macros are ultimately based on maxusers.
  257          * Limit maxproc so that kmap entries cannot be exhausted by
  258          * processes.
  259          */
  260         maxproc = NPROC;
  261         TUNABLE_INT_FETCH("kern.maxproc", &maxproc);
  262         if (maxproc > (physpages / 12))
  263                 maxproc = physpages / 12;
  264         if (maxproc > pid_max)
  265                 maxproc = pid_max;
  266         maxprocperuid = (maxproc * 9) / 10;
  267 
  268         /*
  269          * The default limit for maxfiles is 1/12 of the number of
  270          * physical page but not less than 16 times maxusers.
  271          * At most it can be 1/6 the number of physical pages.
  272          */
  273         maxfiles = imax(MAXFILES, physpages / 8);
  274         TUNABLE_INT_FETCH("kern.maxfiles", &maxfiles);
  275         if (maxfiles > (physpages / 4))
  276                 maxfiles = physpages / 4;
  277         maxfilesperproc = (maxfiles / 10) * 9;
  278         
  279         /*
  280          * Cannot be changed after boot.
  281          */
  282         nbuf = NBUF;
  283         TUNABLE_INT_FETCH("kern.nbuf", &nbuf);
  284         TUNABLE_INT_FETCH("kern.bio_transient_maxcnt", &bio_transient_maxcnt);
  285 
  286         /*
  287          * The default for maxpipekva is min(1/64 of the kernel address space,
  288          * max(1/64 of main memory, 512KB)).  See sys_pipe.c for more details.
  289          */
  290         maxpipekva = (physpages / 64) * PAGE_SIZE;
  291         TUNABLE_LONG_FETCH("kern.ipc.maxpipekva", &maxpipekva);
  292         if (maxpipekva < 512 * 1024)
  293                 maxpipekva = 512 * 1024;
  294         if (maxpipekva > (VM_MAX_KERNEL_ADDRESS - VM_MIN_KERNEL_ADDRESS) / 64)
  295                 maxpipekva = (VM_MAX_KERNEL_ADDRESS - VM_MIN_KERNEL_ADDRESS) /
  296                     64;
  297 }
  298 
  299 /*
  300  * Sysctl stringifying handler for kern.vm_guest.
  301  */
  302 static int
  303 sysctl_kern_vm_guest(SYSCTL_HANDLER_ARGS)
  304 {
  305         return (SYSCTL_OUT(req, vm_guest_sysctl_names[vm_guest], 
  306             strlen(vm_guest_sysctl_names[vm_guest])));
  307 }

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