io/madvise.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright (c) 2004-2005 Silicon Graphics, Inc.
   4  * All Rights Reserved.
   5  */
   6
   7 #include "command.h"
   8 #include "input.h"
   9 #include <sys/mman.h>
  10 #include "init.h"
  11 #include "io.h"
  12
  13 static cmdinfo_t madvise_cmd;
  14
  15 static void
  16 madvise_help(void)
  17 {
  18         printf(_(
  19 "\n"
  20 " advise the page cache about access patterns expected for a mapping\n"
  21 "\n"
  22 " Modifies page cache behavior when operating on the current mapping.\n"
  23 " The range arguments are required by some advise commands ([*] below).\n"
  24 " With no arguments, the POSIX_MADV_NORMAL advice is implied.\n"
  25 " -d -- don't need these pages (POSIX_MADV_DONTNEED) [*]\n"
  26 " -r -- expect random page references (POSIX_MADV_RANDOM)\n"
  27 " -s -- expect sequential page references (POSIX_MADV_SEQUENTIAL)\n"
  28 " -w -- will need these pages (POSIX_MADV_WILLNEED) [*]\n"
  29 " Notes:\n"
  30 "   NORMAL sets the default readahead setting on the file.\n"
  31 "   RANDOM sets the readahead setting on the file to zero.\n"
  32 "   SEQUENTIAL sets double the default readahead setting on the file.\n"
  33 "   WILLNEED forces the maximum readahead.\n"
  34 "\n"));
  35 }
  36
  37 int
  38 madvise_f(
  39         int             argc,
  40         char            **argv)
  41 {
  42         off64_t         offset, llength;
  43         size_t          length;
  44         void            *start;
  45         int             advise = MADV_NORMAL, c;
  46         size_t          blocksize, sectsize;
  47
  48         while ((c = getopt(argc, argv, "drsw")) != EOF) {
  49                 switch (c) {
  50                 case 'd':       /* Don't need these pages */
  51                         advise = MADV_DONTNEED;
  52                         break;
  53                 case 'r':       /* Expect random page references */
  54                         advise = MADV_RANDOM;
  55                         break;
  56                 case 's':       /* Expect sequential page references */
  57                         advise = MADV_SEQUENTIAL;
  58                         break;
  59                 case 'w':       /* Will need these pages */
  60                         advise = MADV_WILLNEED;
  61                         break;
  62                 default:
  63                         return command_usage(&madvise_cmd);
  64                 }
  65         }
  66
  67         if (optind == argc) {
  68                 offset = mapping->offset;
  69                 length = mapping->length;
  70         } else if (optind == argc - 2) {
  71                 init_cvtnum(&blocksize, &sectsize);
  72                 offset = cvtnum(blocksize, sectsize, argv[optind]);
  73                 if (offset < 0) {
  74                         printf(_("non-numeric offset argument -- %s\n"),
  75                                 argv[optind]);
  76                         return 0;
  77                 }
  78                 optind++;
  79                 llength = cvtnum(blocksize, sectsize, argv[optind]);
  80                 if (llength < 0) {
  81                         printf(_("non-numeric length argument -- %s\n"),
  82                                 argv[optind]);
  83                         return 0;
  84                 } else if (llength > (size_t)llength) {
  85                         printf(_("length argument too large -- %lld\n"),
  86                                 (long long)llength);
  87                         return 0;
  88                 } else
  89                         length = (size_t)llength;
  90         } else {
  91                 return command_usage(&madvise_cmd);
  92         }
  93
  94         start = check_mapping_range(mapping, offset, length, 1);
  95         if (!start)
  96                 return 0;
  97
  98         if (madvise(start, length, advise) < 0) {
  99                 perror("madvise");
 100                 return 0;
 101         }
 102         return 0;
 103 }
 104
 105 void
 106 madvise_init(void)
 107 {
 108         madvise_cmd.name = "madvise";
 109         madvise_cmd.altname = "ma";
 110         madvise_cmd.cfunc = madvise_f;
 111         madvise_cmd.argmin = 0;
 112         madvise_cmd.argmax = -1;
 113         madvise_cmd.flags = CMD_NOFILE_OK | CMD_FOREIGN_OK;
 114         madvise_cmd.args = _("[-drsw] [off len]");
 115         madvise_cmd.oneline = _("give advice about use of memory");
 116         madvise_cmd.help = madvise_help;
 117
 118         add_command(&madvise_cmd);
 119 }