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1.7] BUG - GREP slows to a crawl with large number of matches on a single file
- From: aputerguy <nabble at kosowsky dot org>
- To: cygwin at cygwin dot com
- Date: Thu, 5 Nov 2009 15:27:07 -0800 (PST)
- Subject: 1.7] BUG - GREP slows to a crawl with large number of matches on a single file
Running grep on a 20MB file with ~100,000 matches takes an incredible almost
8 minutes under Cygwin 1.7 while taking just 0.2 seconds under Cygwin 1.5
(on a 2nd machine).
The following cases show how grep under 1.7 grinds to a halt as the number
of matches increases.
The data 'testfile' is a plain text file of the acl's of all the 108,000
files on my Windoze computer.
Note since the machines are different, compare relative times across cases
rather than the times between the two machines.
Case 1] Zero matches
time grep "sfsdfdsfds" testfile | wc
0 0 0
Cygwin 1.5
real 0m0.093s
user 0m0.092s
sys 0m0.030s
Cygwin 1.7
real 0m1.353s
user 0m1.342s
sys 0m0.062s
Case 2] One match
time grep ".lesshst" testfile | wc
1 3 29
Cygwin 1.5 (~same as zero matches)
real 0m0.234s
user 0m0.091s
sys 0m0.061s
Cygwin 1.7 (~same as zero matches)
real 0m1.499s
user 0m1.404s
sys 0m0.046s
Case 3] ~1400 matches
Cygwin 1.5 (~ same as zero matches)
time grep ".bin" testfile | wc
1439 5661 71067
real 0m0.110s
user 0m0.076s
sys 0m0.077s
Cygwin 1.7 (~6x zero matches case
real 0m7.537s
user 0m7.341s
sys 0m0.045s
Case 4] ~16000 matches
time grep "Documents and Settings" testfile | wc
15824 131573 1918500
Cygwin 1.5 (~same as zero matches)
real 0m0.437s
user 0m0.092s
sys 0m0.092s
Cygwin 1.7 (~50x zero matches)
real 1m14.491s
user 1m8.904s
sys 0m0.031s
Case 5] ~100,000 matches
time grep "# file" testfile | wc
106988 510944 7930558
Cygwin 1.5 (~1.5x zero matches)
real 0m0.475s
user 0m0.154s
sys 0m0.201s
Cygwin 1.7 (~350x zero matches)
real 7m51.771s
user 7m16.810s
sys 0m0.062s
Case 6] Test that nothing wrong with file system reads or 'wc'
time cat testfile | wc
966300 1821815 20426592
Cygwin 1.5 (approx same time as grepping zero matches)
real 0m0.344s
user 0m0.201s
sys 0m0.186s
Cygwin 1.7 (approx same time as grepping zero matches)
real 0m1.662s
user 0m1.373s
sys 0m0.138s
--
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