Bug #72640 [ReO->Nab]: Regexp with possessive/atomic grouping 25x slower compared to 5.6.x
Edit report at https://bugs.php.net/bug.php?id=72640&edit=1
ID: 72640
Updated by: bwoebi@php.net
Reported by: arjen at parse dot nl
Summary: Regexp with possessive/atomic grouping 25x slower
compared to 5.6.x
-Status: Re-Opened
+Status: Not a bug
Type: Bug
Package: PCRE related
Operating System: Linux
PHP Version: 7.0.9
Block user comment: N
Private report: N
New Comment:
I recommend using (*SKIP) though - this is the fastest you'll get.
preg_replace('~[\pZ\pC]+(*SKIP)$~u', '', str_repeat("\u{2029}", 20000)
. 'x');
Previous Comments:
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[2016-07-21 14:54:14] arjen at parse dot nl
\u{2029} is a PHP7 feature, so test in 5.6 is not the same.. :-/
See https://3v4l.org/7Wfc5/perf#tabs
PHP7 is faster. Regexp still slow, but no regression.
Please close :X
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[2016-07-21 14:22:27] cmb@php.net
> Please take a look at the user time, not at system time.
Ah, you're right!
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[2016-07-21 14:02:59] arjen at parse dot nl
Please take a look at the user time, not at system time.
Or confirm by running it at CLI:
time php -r 'preg_replace("~(?>[\pZ\pC]+)$~u", "",
str_repeat("\u{2029}", 20000) . "x");'
real 0m0.975s
user 0m0.973s
sys 0m0.000s
------------------------------------------------------------------------
[2016-07-21 13:57:59] cmb@php.net
Having a closer look at the performance result shows that PHP
7.0.1 - 7.0.5 appear to be really slow, but that current versions
are not affected, so I'm closing this ticket.
------------------------------------------------------------------------
[2016-07-21 13:10:25] arjen at parse dot nl
Description:
------------
After reading http://stackstatus.net/post/147710624694/outage-postmortem-july-20-2016
we checked our own implementation. We did not use possessive or atomic grouping in our trim regexps,
so one trim call with 20000 whitespace char and a following non-whitespace char took 6 seconds.
After updating the regexp this dropped to 2 seconds. Better but still not safe enough..
So we checked the performance in different php versions on 3v4l.org and 5.6 appeared 25x faster: https://3v4l.org/SPEXB/perf#tabs
Avg 0.066 for 5.6.x compared to 1.670 for 7.0.x
Test script:
---------------
<?php
preg_replace('~(?>[\pZ\pC]+)$~u', '', str_repeat("\u{2029}", 20000)
. 'x');
Expected result:
----------------
Run-time comparable to 5.6.x
Actual result:
--------------
25x slowdown.
------------------------------------------------------------------------
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Edit this bug report at https://bugs.php.net/bug.php?id=72640&edit=1
Thread (9 messages)