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@@ -1,207 +1,210 b'' | |||
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1 | 1 | # worker.py - master-slave parallelism support |
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2 | 2 | # |
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3 | 3 | # Copyright 2013 Facebook, Inc. |
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4 | 4 | # |
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5 | 5 | # This software may be used and distributed according to the terms of the |
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6 | 6 | # GNU General Public License version 2 or any later version. |
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7 | 7 | |
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8 | 8 | from __future__ import absolute_import |
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9 | 9 | |
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10 | 10 | import errno |
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11 | 11 | import os |
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12 | 12 | import signal |
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13 | 13 | import sys |
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14 | 14 | |
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15 | 15 | from .i18n import _ |
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16 | 16 | from . import ( |
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17 | 17 | error, |
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18 | 18 | util, |
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19 | 19 | ) |
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20 | 20 | |
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21 | 21 | def countcpus(): |
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22 | 22 | '''try to count the number of CPUs on the system''' |
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23 | 23 | |
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24 | 24 | # posix |
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25 | 25 | try: |
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26 | 26 | n = int(os.sysconf('SC_NPROCESSORS_ONLN')) |
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27 | 27 | if n > 0: |
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28 | 28 | return n |
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29 | 29 | except (AttributeError, ValueError): |
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30 | 30 | pass |
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31 | 31 | |
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32 | 32 | # windows |
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33 | 33 | try: |
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34 | 34 | n = int(os.environ['NUMBER_OF_PROCESSORS']) |
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35 | 35 | if n > 0: |
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36 | 36 | return n |
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37 | 37 | except (KeyError, ValueError): |
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38 | 38 | pass |
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39 | 39 | |
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40 | 40 | return 1 |
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41 | 41 | |
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42 | 42 | def _numworkers(ui): |
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43 | 43 | s = ui.config('worker', 'numcpus') |
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44 | 44 | if s: |
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45 | 45 | try: |
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46 | 46 | n = int(s) |
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47 | 47 | if n >= 1: |
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48 | 48 | return n |
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49 | 49 | except ValueError: |
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50 | 50 | raise error.Abort(_('number of cpus must be an integer')) |
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51 | 51 | return min(max(countcpus(), 4), 32) |
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52 | 52 | |
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53 | 53 | if os.name == 'posix': |
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54 | 54 | _startupcost = 0.01 |
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55 | 55 | else: |
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56 | 56 | _startupcost = 1e30 |
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57 | 57 | |
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58 | 58 | def worthwhile(ui, costperop, nops): |
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59 | 59 | '''try to determine whether the benefit of multiple processes can |
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60 | 60 | outweigh the cost of starting them''' |
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61 | 61 | linear = costperop * nops |
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62 | 62 | workers = _numworkers(ui) |
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63 | 63 | benefit = linear - (_startupcost * workers + linear / workers) |
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64 | 64 | return benefit >= 0.15 |
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65 | 65 | |
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66 | 66 | def worker(ui, costperarg, func, staticargs, args): |
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67 | 67 | '''run a function, possibly in parallel in multiple worker |
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68 | 68 | processes. |
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69 | 69 | |
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70 | 70 | returns a progress iterator |
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71 | 71 | |
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72 | 72 | costperarg - cost of a single task |
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73 | 73 | |
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74 | 74 | func - function to run |
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75 | 75 | |
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76 | 76 | staticargs - arguments to pass to every invocation of the function |
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77 | 77 | |
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78 | 78 | args - arguments to split into chunks, to pass to individual |
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79 | 79 | workers |
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80 | 80 | ''' |
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81 | 81 | if worthwhile(ui, costperarg, len(args)): |
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82 | 82 | return _platformworker(ui, func, staticargs, args) |
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83 | 83 | return func(*staticargs + (args,)) |
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84 | 84 | |
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85 | 85 | def _posixworker(ui, func, staticargs, args): |
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86 | 86 | rfd, wfd = os.pipe() |
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87 | 87 | workers = _numworkers(ui) |
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88 | 88 | oldhandler = signal.getsignal(signal.SIGINT) |
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89 | 89 | signal.signal(signal.SIGINT, signal.SIG_IGN) |
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90 | 90 | pids, problem = set(), [0] |
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91 | 91 | def killworkers(): |
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92 | 92 | # unregister SIGCHLD handler as all children will be killed. This |
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93 | 93 | # function shouldn't be interrupted by another SIGCHLD; otherwise pids |
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94 | 94 | # could be updated while iterating, which would cause inconsistency. |
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95 | 95 | signal.signal(signal.SIGCHLD, oldchldhandler) |
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96 | 96 | # if one worker bails, there's no good reason to wait for the rest |
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97 | 97 | for p in pids: |
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98 | 98 | try: |
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99 | 99 | os.kill(p, signal.SIGTERM) |
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100 | 100 | except OSError as err: |
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101 | 101 | if err.errno != errno.ESRCH: |
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102 | 102 | raise |
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103 | 103 | def waitforworkers(blocking=True): |
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104 | 104 | for pid in pids.copy(): |
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105 | 105 | p = st = 0 |
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106 | 106 | while True: |
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107 | 107 | try: |
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108 | 108 | p, st = os.waitpid(pid, (0 if blocking else os.WNOHANG)) |
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109 | 109 | break |
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110 | 110 | except OSError as e: |
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111 | 111 | if e.errno == errno.EINTR: |
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112 | 112 | continue |
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113 | 113 | elif e.errno == errno.ECHILD: |
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114 | break # ignore ECHILD | |
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114 | # child would already be reaped, but pids yet been | |
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115 | # updated (maybe interrupted just after waitpid) | |
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116 | pids.discard(pid) | |
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117 | break | |
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115 | 118 | else: |
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116 | 119 | raise |
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117 | 120 | if p: |
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118 |
pids. |
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121 | pids.discard(p) | |
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119 | 122 | st = _exitstatus(st) |
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120 | 123 | if st and not problem[0]: |
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121 | 124 | problem[0] = st |
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122 | 125 | def sigchldhandler(signum, frame): |
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123 | 126 | waitforworkers(blocking=False) |
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124 | 127 | if problem[0]: |
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125 | 128 | killworkers() |
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126 | 129 | oldchldhandler = signal.signal(signal.SIGCHLD, sigchldhandler) |
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127 | 130 | for pargs in partition(args, workers): |
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128 | 131 | pid = os.fork() |
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129 | 132 | if pid == 0: |
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130 | 133 | signal.signal(signal.SIGINT, oldhandler) |
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131 | 134 | signal.signal(signal.SIGCHLD, oldchldhandler) |
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132 | 135 | try: |
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133 | 136 | os.close(rfd) |
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134 | 137 | for i, item in func(*(staticargs + (pargs,))): |
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135 | 138 | os.write(wfd, '%d %s\n' % (i, item)) |
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136 | 139 | os._exit(0) |
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137 | 140 | except KeyboardInterrupt: |
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138 | 141 | os._exit(255) |
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139 | 142 | # other exceptions are allowed to propagate, we rely |
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140 | 143 | # on lock.py's pid checks to avoid release callbacks |
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141 | 144 | pids.add(pid) |
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142 | 145 | os.close(wfd) |
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143 | 146 | fp = os.fdopen(rfd, 'rb', 0) |
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144 | 147 | def cleanup(): |
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145 | 148 | signal.signal(signal.SIGINT, oldhandler) |
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146 | 149 | waitforworkers() |
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147 | 150 | signal.signal(signal.SIGCHLD, oldchldhandler) |
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148 | 151 | status = problem[0] |
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149 | 152 | if status: |
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150 | 153 | if status < 0: |
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151 | 154 | os.kill(os.getpid(), -status) |
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152 | 155 | sys.exit(status) |
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153 | 156 | try: |
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154 | 157 | for line in util.iterfile(fp): |
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155 | 158 | l = line.split(' ', 1) |
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156 | 159 | yield int(l[0]), l[1][:-1] |
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157 | 160 | except: # re-raises |
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158 | 161 | killworkers() |
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159 | 162 | cleanup() |
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160 | 163 | raise |
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161 | 164 | cleanup() |
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162 | 165 | |
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163 | 166 | def _posixexitstatus(code): |
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164 | 167 | '''convert a posix exit status into the same form returned by |
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165 | 168 | os.spawnv |
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166 | 169 | |
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167 | 170 | returns None if the process was stopped instead of exiting''' |
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168 | 171 | if os.WIFEXITED(code): |
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169 | 172 | return os.WEXITSTATUS(code) |
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170 | 173 | elif os.WIFSIGNALED(code): |
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171 | 174 | return -os.WTERMSIG(code) |
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172 | 175 | |
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173 | 176 | if os.name != 'nt': |
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174 | 177 | _platformworker = _posixworker |
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175 | 178 | _exitstatus = _posixexitstatus |
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176 | 179 | |
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177 | 180 | def partition(lst, nslices): |
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178 | 181 | '''partition a list into N slices of roughly equal size |
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179 | 182 | |
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180 | 183 | The current strategy takes every Nth element from the input. If |
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181 | 184 | we ever write workers that need to preserve grouping in input |
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182 | 185 | we should consider allowing callers to specify a partition strategy. |
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183 | 186 | |
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184 | 187 | mpm is not a fan of this partitioning strategy when files are involved. |
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185 | 188 | In his words: |
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186 | 189 | |
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187 | 190 | Single-threaded Mercurial makes a point of creating and visiting |
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188 | 191 | files in a fixed order (alphabetical). When creating files in order, |
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189 | 192 | a typical filesystem is likely to allocate them on nearby regions on |
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190 | 193 | disk. Thus, when revisiting in the same order, locality is maximized |
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191 | 194 | and various forms of OS and disk-level caching and read-ahead get a |
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192 | 195 | chance to work. |
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193 | 196 | |
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194 | 197 | This effect can be quite significant on spinning disks. I discovered it |
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195 | 198 | circa Mercurial v0.4 when revlogs were named by hashes of filenames. |
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196 | 199 | Tarring a repo and copying it to another disk effectively randomized |
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197 | 200 | the revlog ordering on disk by sorting the revlogs by hash and suddenly |
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198 | 201 | performance of my kernel checkout benchmark dropped by ~10x because the |
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199 | 202 | "working set" of sectors visited no longer fit in the drive's cache and |
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200 | 203 | the workload switched from streaming to random I/O. |
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201 | 204 | |
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202 | 205 | What we should really be doing is have workers read filenames from a |
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203 | 206 | ordered queue. This preserves locality and also keeps any worker from |
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204 | 207 | getting more than one file out of balance. |
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205 | 208 | ''' |
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206 | 209 | for i in range(nslices): |
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207 | 210 | yield lst[i::nslices] |
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