linux/kernel/timeconst.pl
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   1#!/usr/bin/perl
   2# -----------------------------------------------------------------------
   3#
   4#   Copyright 2007-2008 rPath, Inc. - All Rights Reserved
   5#
   6#   This file is part of the Linux kernel, and is made available under
   7#   the terms of the GNU General Public License version 2 or (at your
   8#   option) any later version; incorporated herein by reference.
   9#
  10# -----------------------------------------------------------------------
  11#
  12
  13#
  14# Usage: timeconst.pl HZ > timeconst.h
  15#
  16
  17# Precomputed values for systems without Math::BigInt
  18# Generated by:
  19# timeconst.pl --can 24 32 48 64 100 122 128 200 250 256 300 512 1000 1024 1200
  20%canned_values = (
  21        24 => [
  22                '0xa6aaaaab','0x2aaaaaa',26,
  23                125,3,
  24                '0xc49ba5e4','0x1fbe76c8b4',37,
  25                3,125,
  26                '0xa2c2aaab','0xaaaa',16,
  27                125000,3,
  28                '0xc9539b89','0x7fffbce4217d',47,
  29                3,125000,
  30        ], 32 => [
  31                '0xfa000000','0x6000000',27,
  32                125,4,
  33                '0x83126e98','0xfdf3b645a',36,
  34                4,125,
  35                '0xf4240000','0x0',17,
  36                31250,1,
  37                '0x8637bd06','0x3fff79c842fa',46,
  38                1,31250,
  39        ], 48 => [
  40                '0xa6aaaaab','0x6aaaaaa',27,
  41                125,6,
  42                '0xc49ba5e4','0xfdf3b645a',36,
  43                6,125,
  44                '0xa2c2aaab','0x15555',17,
  45                62500,3,
  46                '0xc9539b89','0x3fffbce4217d',46,
  47                3,62500,
  48        ], 64 => [
  49                '0xfa000000','0xe000000',28,
  50                125,8,
  51                '0x83126e98','0x7ef9db22d',35,
  52                8,125,
  53                '0xf4240000','0x0',18,
  54                15625,1,
  55                '0x8637bd06','0x1fff79c842fa',45,
  56                1,15625,
  57        ], 100 => [
  58                '0xa0000000','0x0',28,
  59                10,1,
  60                '0xcccccccd','0x733333333',35,
  61                1,10,
  62                '0x9c400000','0x0',18,
  63                10000,1,
  64                '0xd1b71759','0x1fff2e48e8a7',45,
  65                1,10000,
  66        ], 122 => [
  67                '0x8325c53f','0xfbcda3a',28,
  68                500,61,
  69                '0xf9db22d1','0x7fbe76c8b',35,
  70                61,500,
  71                '0x8012e2a0','0x3ef36',18,
  72                500000,61,
  73                '0xffda4053','0x1ffffbce4217',45,
  74                61,500000,
  75        ], 128 => [
  76                '0xfa000000','0x1e000000',29,
  77                125,16,
  78                '0x83126e98','0x3f7ced916',34,
  79                16,125,
  80                '0xf4240000','0x40000',19,
  81                15625,2,
  82                '0x8637bd06','0xfffbce4217d',44,
  83                2,15625,
  84        ], 200 => [
  85                '0xa0000000','0x0',29,
  86                5,1,
  87                '0xcccccccd','0x333333333',34,
  88                1,5,
  89                '0x9c400000','0x0',19,
  90                5000,1,
  91                '0xd1b71759','0xfff2e48e8a7',44,
  92                1,5000,
  93        ], 250 => [
  94                '0x80000000','0x0',29,
  95                4,1,
  96                '0x80000000','0x180000000',33,
  97                1,4,
  98                '0xfa000000','0x0',20,
  99                4000,1,
 100                '0x83126e98','0x7ff7ced9168',43,
 101                1,4000,
 102        ], 256 => [
 103                '0xfa000000','0x3e000000',30,
 104                125,32,
 105                '0x83126e98','0x1fbe76c8b',33,
 106                32,125,
 107                '0xf4240000','0xc0000',20,
 108                15625,4,
 109                '0x8637bd06','0x7ffde7210be',43,
 110                4,15625,
 111        ], 300 => [
 112                '0xd5555556','0x2aaaaaaa',30,
 113                10,3,
 114                '0x9999999a','0x1cccccccc',33,
 115                3,10,
 116                '0xd0555556','0xaaaaa',20,
 117                10000,3,
 118                '0x9d495183','0x7ffcb923a29',43,
 119                3,10000,
 120        ], 512 => [
 121                '0xfa000000','0x7e000000',31,
 122                125,64,
 123                '0x83126e98','0xfdf3b645',32,
 124                64,125,
 125                '0xf4240000','0x1c0000',21,
 126                15625,8,
 127                '0x8637bd06','0x3ffef39085f',42,
 128                8,15625,
 129        ], 1000 => [
 130                '0x80000000','0x0',31,
 131                1,1,
 132                '0x80000000','0x0',31,
 133                1,1,
 134                '0xfa000000','0x0',22,
 135                1000,1,
 136                '0x83126e98','0x1ff7ced9168',41,
 137                1,1000,
 138        ], 1024 => [
 139                '0xfa000000','0xfe000000',32,
 140                125,128,
 141                '0x83126e98','0x7ef9db22',31,
 142                128,125,
 143                '0xf4240000','0x3c0000',22,
 144                15625,16,
 145                '0x8637bd06','0x1fff79c842f',41,
 146                16,15625,
 147        ], 1200 => [
 148                '0xd5555556','0xd5555555',32,
 149                5,6,
 150                '0x9999999a','0x66666666',31,
 151                6,5,
 152                '0xd0555556','0x2aaaaa',22,
 153                2500,3,
 154                '0x9d495183','0x1ffcb923a29',41,
 155                3,2500,
 156        ]
 157);
 158
 159$has_bigint = eval 'use Math::BigInt qw(bgcd); 1;';
 160
 161sub bint($)
 162{
 163        my($x) = @_;
 164        return Math::BigInt->new($x);
 165}
 166
 167#
 168# Constants for division by reciprocal multiplication.
 169# (bits, numerator, denominator)
 170#
 171sub fmul($$$)
 172{
 173        my ($b,$n,$d) = @_;
 174
 175        $n = bint($n);
 176        $d = bint($d);
 177
 178        return scalar (($n << $b)+$d-bint(1))/$d;
 179}
 180
 181sub fadj($$$)
 182{
 183        my($b,$n,$d) = @_;
 184
 185        $n = bint($n);
 186        $d = bint($d);
 187
 188        $d = $d/bgcd($n, $d);
 189        return scalar (($d-bint(1)) << $b)/$d;
 190}
 191
 192sub fmuls($$$) {
 193        my($b,$n,$d) = @_;
 194        my($s,$m);
 195        my($thres) = bint(1) << ($b-1);
 196
 197        $n = bint($n);
 198        $d = bint($d);
 199
 200        for ($s = 0; 1; $s++) {
 201                $m = fmul($s,$n,$d);
 202                return $s if ($m >= $thres);
 203        }
 204        return 0;
 205}
 206
 207# Generate a hex value if the result fits in 64 bits;
 208# otherwise skip.
 209sub bignum_hex($) {
 210        my($x) = @_;
 211        my $s = $x->as_hex();
 212
 213        return (length($s) > 18) ? undef : $s;
 214}
 215
 216# Provides mul, adj, and shr factors for a specific
 217# (bit, time, hz) combination
 218sub muladj($$$) {
 219        my($b, $t, $hz) = @_;
 220        my $s = fmuls($b, $t, $hz);
 221        my $m = fmul($s, $t, $hz);
 222        my $a = fadj($s, $t, $hz);
 223        return (bignum_hex($m), bignum_hex($a), $s);
 224}
 225
 226# Provides numerator, denominator values
 227sub numden($$) {
 228        my($n, $d) = @_;
 229        my $g = bgcd($n, $d);
 230        return ($n/$g, $d/$g);
 231}
 232
 233# All values for a specific (time, hz) combo
 234sub conversions($$) {
 235        my ($t, $hz) = @_;
 236        my @val = ();
 237
 238        # HZ_TO_xx
 239        push(@val, muladj(32, $t, $hz));
 240        push(@val, numden($t, $hz));
 241
 242        # xx_TO_HZ
 243        push(@val, muladj(32, $hz, $t));
 244        push(@val, numden($hz, $t));
 245
 246        return @val;
 247}
 248
 249sub compute_values($) {
 250        my($hz) = @_;
 251        my @val = ();
 252        my $s, $m, $a, $g;
 253
 254        if (!$has_bigint) {
 255                die "$0: HZ == $hz not canned and ".
 256                    "Math::BigInt not available\n";
 257        }
 258
 259        # MSEC conversions
 260        push(@val, conversions(1000, $hz));
 261
 262        # USEC conversions
 263        push(@val, conversions(1000000, $hz));
 264
 265        return @val;
 266}
 267
 268sub outputval($$)
 269{
 270        my($name, $val) = @_;
 271        my $csuf;
 272
 273        if (defined($val)) {
 274            if ($name !~ /SHR/) {
 275                $val = "U64_C($val)";
 276            }
 277            printf "#define %-23s %s\n", $name.$csuf, $val.$csuf;
 278        }
 279}
 280
 281sub output($@)
 282{
 283        my($hz, @val) = @_;
 284        my $pfx, $bit, $suf, $s, $m, $a;
 285
 286        print "/* Automatically generated by kernel/timeconst.pl */\n";
 287        print "/* Conversion constants for HZ == $hz */\n";
 288        print "\n";
 289        print "#ifndef KERNEL_TIMECONST_H\n";
 290        print "#define KERNEL_TIMECONST_H\n";
 291        print "\n";
 292
 293        print "#include <linux/param.h>\n";
 294        print "#include <linux/types.h>\n";
 295
 296        print "\n";
 297        print "#if HZ != $hz\n";
 298        print "#error \"kernel/timeconst.h has the wrong HZ value!\"\n";
 299        print "#endif\n";
 300        print "\n";
 301
 302        foreach $pfx ('HZ_TO_MSEC','MSEC_TO_HZ',
 303                      'HZ_TO_USEC','USEC_TO_HZ') {
 304                foreach $bit (32) {
 305                        foreach $suf ('MUL', 'ADJ', 'SHR') {
 306                                outputval("${pfx}_$suf$bit", shift(@val));
 307                        }
 308                }
 309                foreach $suf ('NUM', 'DEN') {
 310                        outputval("${pfx}_$suf", shift(@val));
 311                }
 312        }
 313
 314        print "\n";
 315        print "#endif /* KERNEL_TIMECONST_H */\n";
 316}
 317
 318# Pretty-print Perl values
 319sub perlvals(@) {
 320        my $v;
 321        my @l = ();
 322
 323        foreach $v (@_) {
 324                if (!defined($v)) {
 325                        push(@l, 'undef');
 326                } elsif ($v =~ /^0x/) {
 327                        push(@l, "\'".$v."\'");
 328                } else {
 329                        push(@l, $v.'');
 330                }
 331        }
 332        return join(',', @l);
 333}
 334
 335($hz) = @ARGV;
 336
 337# Use this to generate the %canned_values structure
 338if ($hz eq '--can') {
 339        shift(@ARGV);
 340        @hzlist = sort {$a <=> $b} (@ARGV);
 341
 342        print "# Precomputed values for systems without Math::BigInt\n";
 343        print "# Generated by:\n";
 344        print "# timeconst.pl --can ", join(' ', @hzlist), "\n";
 345        print "\%canned_values = (\n";
 346        my $pf = "\t";
 347        foreach $hz (@hzlist) {
 348                my @values = compute_values($hz);
 349                print "$pf$hz => [\n";
 350                while (scalar(@values)) {
 351                        my $bit;
 352                        foreach $bit (32) {
 353                                my $m = shift(@values);
 354                                my $a = shift(@values);
 355                                my $s = shift(@values);
 356                                print "\t\t", perlvals($m,$a,$s), ",\n";
 357                        }
 358                        my $n = shift(@values);
 359                        my $d = shift(@values);
 360                        print "\t\t", perlvals($n,$d), ",\n";
 361                }
 362                print "\t]";
 363                $pf = ', ';
 364        }
 365        print "\n);\n";
 366} else {
 367        $hz += 0;                       # Force to number
 368        if ($hz < 1) {
 369                die "Usage: $0 HZ\n";
 370        }
 371
 372        @val = @{$canned_values{$hz}};
 373        if (!defined(@val)) {
 374                @val = compute_values($hz);
 375        }
 376        output($hz, @val);
 377}
 378exit 0;
 379
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