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/9/sys/kern/subr_param.c 257433 2013-10-31 10:14:12Z 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 (maxproc * 2)
   80 #endif
   81 
   82 static int sysctl_kern_vm_guest(SYSCTL_HANDLER_ARGS);
   83 
   84 int     hz;
   85 int     tick;
   86 int     maxusers;                       /* base tunable */
   87 int     maxproc;                        /* maximum # of processes */
   88 int     maxprocperuid;                  /* max # of procs per user */
   89 int     maxfiles;                       /* sys. wide open files limit */
   90 int     maxfilesperproc;                /* per-proc open files limit */
   91 int     msgbufsize;                     /* size of kernel message buffer */
   92 int     ncallout;                       /* maximum # of timer events */
   93 int     nbuf;
   94 int     bio_transient_maxcnt;
   95 int     ngroups_max;                    /* max # groups per process */
   96 int     nswbuf;
   97 pid_t   pid_max = PID_MAX;
   98 long    maxswzone;                      /* max swmeta KVA storage */
   99 long    maxbcache;                      /* max buffer cache KVA storage */
  100 long    maxpipekva;                     /* Limit on pipe KVA */
  101 int     vm_guest;                       /* Running as virtual machine guest? */
  102 u_long  maxtsiz;                        /* max text size */
  103 u_long  dfldsiz;                        /* initial data size limit */
  104 u_long  maxdsiz;                        /* max data size */
  105 u_long  dflssiz;                        /* initial stack size limit */
  106 u_long  maxssiz;                        /* max stack size */
  107 u_long  sgrowsiz;                       /* amount to grow stack */
  108 
  109 SYSCTL_INT(_kern, OID_AUTO, hz, CTLFLAG_RDTUN, &hz, 0,
  110     "Number of clock ticks per second");
  111 SYSCTL_INT(_kern, OID_AUTO, ncallout, CTLFLAG_RDTUN, &ncallout, 0,
  112     "Number of pre-allocated timer events");
  113 SYSCTL_INT(_kern, OID_AUTO, nbuf, CTLFLAG_RDTUN, &nbuf, 0,
  114     "Number of buffers in the buffer cache");
  115 SYSCTL_INT(_kern, OID_AUTO, nswbuf, CTLFLAG_RDTUN, &nswbuf, 0,
  116     "Number of swap buffers");
  117 SYSCTL_INT(_kern, OID_AUTO, msgbufsize, CTLFLAG_RDTUN, &msgbufsize, 0,
  118     "Size of the kernel message buffer");
  119 SYSCTL_LONG(_kern, OID_AUTO, maxswzone, CTLFLAG_RDTUN, &maxswzone, 0,
  120     "Maximum memory for swap metadata");
  121 SYSCTL_LONG(_kern, OID_AUTO, maxbcache, CTLFLAG_RDTUN, &maxbcache, 0,
  122     "Maximum value of vfs.maxbufspace");
  123 SYSCTL_INT(_kern, OID_AUTO, bio_transient_maxcnt, CTLFLAG_RDTUN,
  124     &bio_transient_maxcnt, 0,
  125     "Maximum number of transient BIOs mappings");
  126 SYSCTL_ULONG(_kern, OID_AUTO, maxtsiz, CTLFLAG_RW | CTLFLAG_TUN, &maxtsiz, 0,
  127     "Maximum text size");
  128 SYSCTL_ULONG(_kern, OID_AUTO, dfldsiz, CTLFLAG_RW | CTLFLAG_TUN, &dfldsiz, 0,
  129     "Initial data size limit");
  130 SYSCTL_ULONG(_kern, OID_AUTO, maxdsiz, CTLFLAG_RW | CTLFLAG_TUN, &maxdsiz, 0,
  131     "Maximum data size");
  132 SYSCTL_ULONG(_kern, OID_AUTO, dflssiz, CTLFLAG_RW | CTLFLAG_TUN, &dflssiz, 0,
  133     "Initial stack size limit");
  134 SYSCTL_ULONG(_kern, OID_AUTO, maxssiz, CTLFLAG_RW | CTLFLAG_TUN, &maxssiz, 0,
  135     "Maximum stack size");
  136 SYSCTL_ULONG(_kern, OID_AUTO, sgrowsiz, CTLFLAG_RW | CTLFLAG_TUN, &sgrowsiz, 0,
  137     "Amount to grow stack on a stack fault");
  138 SYSCTL_PROC(_kern, OID_AUTO, vm_guest, CTLFLAG_RD | CTLTYPE_STRING,
  139     NULL, 0, sysctl_kern_vm_guest, "A",
  140     "Virtual machine guest detected? (none|generic|xen)");
  141 
  142 /*
  143  * These have to be allocated somewhere; allocating
  144  * them here forces loader errors if this file is omitted
  145  * (if they've been externed everywhere else; hah!).
  146  */
  147 struct  buf *swbuf;
  148 
  149 /*
  150  * The elements of this array are ordered based upon the values of the
  151  * corresponding enum VM_GUEST members.
  152  */
  153 static const char *const vm_guest_sysctl_names[] = {
  154         "none",
  155         "generic",
  156         "xen",
  157         NULL
  158 };
  159 
  160 #ifndef XEN
  161 static const char *const vm_bnames[] = {
  162         "QEMU",                         /* QEMU */
  163         "Plex86",                       /* Plex86 */
  164         "Bochs",                        /* Bochs */
  165         "Xen",                          /* Xen */
  166         "BHYVE",                        /* bhyve */
  167         "Seabios",                      /* KVM */
  168         NULL
  169 };
  170 
  171 static const char *const vm_pnames[] = {
  172         "VMware Virtual Platform",      /* VMWare VM */
  173         "Virtual Machine",              /* Microsoft VirtualPC */
  174         "VirtualBox",                   /* Sun xVM VirtualBox */
  175         "Parallels Virtual Platform",   /* Parallels VM */
  176         "KVM",                          /* KVM */
  177         NULL
  178 };
  179 
  180 
  181 /*
  182  * Detect known Virtual Machine hosts by inspecting the emulated BIOS.
  183  */
  184 static enum VM_GUEST
  185 detect_virtual(void)
  186 {
  187         char *sysenv;
  188         int i;
  189 
  190         sysenv = getenv("smbios.bios.vendor");
  191         if (sysenv != NULL) {
  192                 for (i = 0; vm_bnames[i] != NULL; i++)
  193                         if (strcmp(sysenv, vm_bnames[i]) == 0) {
  194                                 freeenv(sysenv);
  195                                 return (VM_GUEST_VM);
  196                         }
  197                 freeenv(sysenv);
  198         }
  199         sysenv = getenv("smbios.system.product");
  200         if (sysenv != NULL) {
  201                 for (i = 0; vm_pnames[i] != NULL; i++)
  202                         if (strcmp(sysenv, vm_pnames[i]) == 0) {
  203                                 freeenv(sysenv);
  204                                 return (VM_GUEST_VM);
  205                         }
  206                 freeenv(sysenv);
  207         }
  208         return (VM_GUEST_NO);
  209 }
  210 #endif
  211 
  212 /*
  213  * Boot time overrides that are not scaled against main memory
  214  */
  215 void
  216 init_param1(void)
  217 {
  218 #ifndef XEN
  219         vm_guest = detect_virtual();
  220 #else
  221         vm_guest = VM_GUEST_XEN;
  222 #endif
  223         hz = -1;
  224         TUNABLE_INT_FETCH("kern.hz", &hz);
  225         if (hz == -1)
  226                 hz = vm_guest > VM_GUEST_NO ? HZ_VM : HZ;
  227         tick = 1000000 / hz;
  228 
  229 #ifdef VM_SWZONE_SIZE_MAX
  230         maxswzone = VM_SWZONE_SIZE_MAX;
  231 #endif
  232         TUNABLE_LONG_FETCH("kern.maxswzone", &maxswzone);
  233 #ifdef VM_BCACHE_SIZE_MAX
  234         maxbcache = VM_BCACHE_SIZE_MAX;
  235 #endif
  236         TUNABLE_LONG_FETCH("kern.maxbcache", &maxbcache);
  237         msgbufsize = MSGBUF_SIZE;
  238         TUNABLE_INT_FETCH("kern.msgbufsize", &msgbufsize);
  239 
  240         maxtsiz = MAXTSIZ;
  241         TUNABLE_ULONG_FETCH("kern.maxtsiz", &maxtsiz);
  242         dfldsiz = DFLDSIZ;
  243         TUNABLE_ULONG_FETCH("kern.dfldsiz", &dfldsiz);
  244         maxdsiz = MAXDSIZ;
  245         TUNABLE_ULONG_FETCH("kern.maxdsiz", &maxdsiz);
  246         dflssiz = DFLSSIZ;
  247         TUNABLE_ULONG_FETCH("kern.dflssiz", &dflssiz);
  248         maxssiz = MAXSSIZ;
  249         TUNABLE_ULONG_FETCH("kern.maxssiz", &maxssiz);
  250         sgrowsiz = SGROWSIZ;
  251         TUNABLE_ULONG_FETCH("kern.sgrowsiz", &sgrowsiz);
  252 
  253         /*
  254          * Let the administrator set {NGROUPS_MAX}, but disallow values
  255          * less than NGROUPS_MAX which would violate POSIX.1-2008 or
  256          * greater than INT_MAX-1 which would result in overflow.
  257          */
  258         ngroups_max = NGROUPS_MAX;
  259         TUNABLE_INT_FETCH("kern.ngroups", &ngroups_max);
  260         if (ngroups_max < NGROUPS_MAX)
  261                 ngroups_max = NGROUPS_MAX;
  262 
  263         /*
  264          * Only allow to lower the maximal pid.
  265          * Prevent setting up a non-bootable system if pid_max is too low.
  266          */
  267         TUNABLE_INT_FETCH("kern.pid_max", &pid_max);
  268         if (pid_max > PID_MAX)
  269                 pid_max = PID_MAX;
  270         else if (pid_max < 300)
  271                 pid_max = 300;
  272 
  273         TUNABLE_INT_FETCH("vfs.unmapped_buf_allowed", &unmapped_buf_allowed);
  274 }
  275 
  276 /*
  277  * Boot time overrides that are scaled against main memory
  278  */
  279 void
  280 init_param2(long physpages)
  281 {
  282 
  283         /* Base parameters */
  284         maxusers = MAXUSERS;
  285         TUNABLE_INT_FETCH("kern.maxusers", &maxusers);
  286         if (maxusers == 0) {
  287                 maxusers = physpages / (2 * 1024 * 1024 / PAGE_SIZE);
  288                 if (maxusers < 32)
  289                         maxusers = 32;
  290 #ifdef VM_MAX_AUTOTUNE_MAXUSERS
  291                 if (maxusers > VM_MAX_AUTOTUNE_MAXUSERS)
  292                         maxusers = VM_MAX_AUTOTUNE_MAXUSERS;
  293 #endif
  294                 /*
  295                  * Scales down the function in which maxusers grows once
  296                  * we hit 384.
  297                  */
  298                 if (maxusers > 384)
  299                         maxusers = 384 + ((maxusers - 384) / 8);
  300         }
  301 
  302         /*
  303          * The following can be overridden after boot via sysctl.  Note:
  304          * unless overriden, these macros are ultimately based on maxusers.
  305          * Limit maxproc so that kmap entries cannot be exhausted by
  306          * processes.
  307          */
  308         maxproc = NPROC;
  309         TUNABLE_INT_FETCH("kern.maxproc", &maxproc);
  310         if (maxproc > (physpages / 12))
  311                 maxproc = physpages / 12;
  312         maxprocperuid = (maxproc * 9) / 10;
  313 
  314         /*
  315          * The default limit for maxfiles is 1/12 of the number of
  316          * physical page but not less than 16 times maxusers.
  317          * At most it can be 1/6 the number of physical pages.
  318          */
  319         maxfiles = imax(MAXFILES, physpages / 8);
  320         TUNABLE_INT_FETCH("kern.maxfiles", &maxfiles);
  321         if (maxfiles > (physpages / 4))
  322                 maxfiles = physpages / 4;
  323         maxfilesperproc = (maxfiles / 10) * 9;
  324         
  325         /*
  326          * Cannot be changed after boot.
  327          */
  328         nbuf = NBUF;
  329         TUNABLE_INT_FETCH("kern.nbuf", &nbuf);
  330         TUNABLE_INT_FETCH("kern.bio_transient_maxcnt", &bio_transient_maxcnt);
  331 
  332         /*
  333          * XXX: Does the callout wheel have to be so big?
  334          *
  335          * Clip callout to result of previous function of maxusers maximum
  336          * 384.  This is still huge, but acceptable.
  337          */
  338         ncallout = imin(16 + maxproc + maxfiles, 18508);
  339         TUNABLE_INT_FETCH("kern.ncallout", &ncallout);
  340 
  341         /*
  342          * The default for maxpipekva is min(1/64 of the kernel address space,
  343          * max(1/64 of main memory, 512KB)).  See sys_pipe.c for more details.
  344          */
  345         maxpipekva = (physpages / 64) * PAGE_SIZE;
  346         TUNABLE_LONG_FETCH("kern.ipc.maxpipekva", &maxpipekva);
  347         if (maxpipekva < 512 * 1024)
  348                 maxpipekva = 512 * 1024;
  349         if (maxpipekva > (VM_MAX_KERNEL_ADDRESS - VM_MIN_KERNEL_ADDRESS) / 64)
  350                 maxpipekva = (VM_MAX_KERNEL_ADDRESS - VM_MIN_KERNEL_ADDRESS) /
  351                     64;
  352 }
  353 
  354 /*
  355  * Sysctl stringifying handler for kern.vm_guest.
  356  */
  357 static int
  358 sysctl_kern_vm_guest(SYSCTL_HANDLER_ARGS)
  359 {
  360         return (SYSCTL_OUT(req, vm_guest_sysctl_names[vm_guest], 
  361             strlen(vm_guest_sysctl_names[vm_guest])));
  362 }

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