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154 lines
4.1 KiB
Python
154 lines
4.1 KiB
Python
# A parallelized "find(1)" using the thread module.
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# This demonstrates the use of a work queue and worker threads.
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# It really does do more stats/sec when using multiple threads,
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# although the improvement is only about 20-30 percent.
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# (That was 8 years ago. In 2002, on Linux, I can't measure
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# a speedup. :-( )
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# I'm too lazy to write a command line parser for the full find(1)
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# command line syntax, so the predicate it searches for is wired-in,
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# see function selector() below. (It currently searches for files with
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# world write permission.)
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# Usage: parfind.py [-w nworkers] [directory] ...
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# Default nworkers is 4
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import sys
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import getopt
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import time
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import os
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from stat import *
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import _thread as thread
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# Work queue class. Usage:
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# wq = WorkQ()
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# wq.addwork(func, (arg1, arg2, ...)) # one or more calls
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# wq.run(nworkers)
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# The work is done when wq.run() completes.
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# The function calls executed by the workers may add more work.
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# Don't use keyboard interrupts!
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class WorkQ:
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# Invariants:
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# - busy and work are only modified when mutex is locked
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# - len(work) is the number of jobs ready to be taken
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# - busy is the number of jobs being done
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# - todo is locked iff there is no work and somebody is busy
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def __init__(self):
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self.mutex = thread.allocate()
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self.todo = thread.allocate()
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self.todo.acquire()
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self.work = []
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self.busy = 0
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def addwork(self, func, args):
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job = (func, args)
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self.mutex.acquire()
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self.work.append(job)
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self.mutex.release()
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if len(self.work) == 1:
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self.todo.release()
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def _getwork(self):
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self.todo.acquire()
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self.mutex.acquire()
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if self.busy == 0 and len(self.work) == 0:
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self.mutex.release()
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self.todo.release()
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return None
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job = self.work[0]
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del self.work[0]
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self.busy = self.busy + 1
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self.mutex.release()
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if len(self.work) > 0:
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self.todo.release()
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return job
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def _donework(self):
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self.mutex.acquire()
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self.busy = self.busy - 1
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if self.busy == 0 and len(self.work) == 0:
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self.todo.release()
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self.mutex.release()
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def _worker(self):
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time.sleep(0.00001) # Let other threads run
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while 1:
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job = self._getwork()
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if not job:
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break
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func, args = job
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func(*args)
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self._donework()
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def run(self, nworkers):
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if not self.work:
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return # Nothing to do
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for i in range(nworkers-1):
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thread.start_new(self._worker, ())
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self._worker()
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self.todo.acquire()
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# Main program
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def main():
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nworkers = 4
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opts, args = getopt.getopt(sys.argv[1:], '-w:')
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for opt, arg in opts:
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if opt == '-w':
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nworkers = int(arg)
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if not args:
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args = [os.curdir]
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wq = WorkQ()
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for dir in args:
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wq.addwork(find, (dir, selector, wq))
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t1 = time.time()
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wq.run(nworkers)
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t2 = time.time()
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sys.stderr.write('Total time %r sec.\n' % (t2-t1))
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# The predicate -- defines what files we look for.
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# Feel free to change this to suit your purpose
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def selector(dir, name, fullname, stat):
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# Look for world writable files that are not symlinks
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return (stat[ST_MODE] & 0o002) != 0 and not S_ISLNK(stat[ST_MODE])
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# The find procedure -- calls wq.addwork() for subdirectories
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def find(dir, pred, wq):
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try:
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names = os.listdir(dir)
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except os.error as msg:
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print(repr(dir), ':', msg)
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return
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for name in names:
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if name not in (os.curdir, os.pardir):
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fullname = os.path.join(dir, name)
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try:
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stat = os.lstat(fullname)
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except os.error as msg:
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print(repr(fullname), ':', msg)
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continue
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if pred(dir, name, fullname, stat):
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print(fullname)
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if S_ISDIR(stat[ST_MODE]):
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if not os.path.ismount(fullname):
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wq.addwork(find, (fullname, pred, wq))
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# Call the main program
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main()
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