Bug #79519 [Opn]: Memory leak in PHP 7.4

From: Date: Fri, 15 May 2020 09:22:42 +0000
Subject: Bug #79519 [Opn]: Memory leak in PHP 7.4
References: 1  Groups: php.bugs 
Request: Send a blank email to php-bugs+get-227050@lists.php.net to get a copy of this message 
Edit report at https://bugs.php.net/bug.php?id=79519&edit=1

 ID:                 79519
 Updated by:         nikic@php.net
 Reported by:        kieran at miami-nice dot co dot uk
 Summary:            Memory leak in PHP 7.4
 Status:             Open
 Type:               Bug
 Package:            Performance problem
 Operating System:   Linux
 PHP Version:        7.4.5
 Block user comment: N
 Private report:     N

 New Comment:

@kieran: PHP 7.4 fixed some issues related to anonymous functions "overwriting" previous
anonymous functions in the same file under some circumstances. Unfortunately this also means that
this leak is now more pronounced, because this accidental destruction vector no longer exists.


Previous Comments:
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[2020-05-15 09:16:40] kieran at supportpal dot com

I thought it might be that too, but it seems odd that 7.4 is so much higher when that bug report
suggests the issue exists in most of 7.x

Nothing in the ms_print in my previous message?

I'll check if includes can be memorised.

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[2020-05-15 08:54:12] nikic@php.net

@kieran: The "factories" case looks like https://bugs.php.net/bug.php?id=76982, where a
file declaring an anonymous function is included many times. The anonymous function declaration will
leak in that case. This is a bug in PHP, but not one that will be fixed in 7.4. I'm not
familiar with Laravel's factory system, but it can probably be addressed there by making that
the includes are memoized.

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[2020-05-08 18:23:16] kieran at supportpal dot com

Here's the result from valgrind on the CI server (nothing to do with my reproducers). Anything
jump out Nikita? Not sure why it's blanked a lot of the lines - it's running with
--enable-debug

$ USE_ZEND_ALLOC=0 valgrind --tool=massif php vendor/phpunit/phpunit/phpunit
 ==25== Massif, a heap profiler
 ==25== Copyright (C) 2003-2017, and GNU GPL'd, by Nicholas Nethercote
 ==25== Using Valgrind-3.14.0 and LibVEX; rerun with -h for copyright info
 ==25== Command: php vendor/phpunit/phpunit/phpunit
 ==25== 
 PHPUnit 8.5.4 by Sebastian Bergmann and contributors.

https://gist.githubusercontent.com/bytestream/ad3270993599c720eb7db8ada597eb24/raw/fe94995d1aee1eb64a9e61da07810717fb32e0da/massif.out.25

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[2020-05-05 12:07:08] jerome dot vieilledent at blackfire dot io

It seems that my profile comparisons are not easy to share, so I did some screenshots which you can
view here: https://github.com/bytestream/php74-memory-leak/issues/1

------------------------------------------------------------------------
[2020-05-05 09:25:22] jerome dot vieilledent at blackfire dot io

Hi there,

Here are 2 profiles for comparison:

- PHP 7.3.17: https://blackfire.io/profiles/b7785fda-415f-4176-a57e-f5e2417b46b0/graph
- PHP 7.4.5: https://blackfire.io/profiles/712b3b08-4ccc-4a6a-ae9b-70b4ee030334/graph
- Comparison graph:https://blackfire.io/profiles/compare/b7785fda-415f-4176-a57e-f5e2417b46b0...712b3b08-4ccc-4a6a-ae9b-70b4ee030334/graph

You have access to the timeline which shows the peak memory increasing (blue graph in the
background).
While exploring the comparison graph a bit, using the memory dimension, I found that it looks like
it's coming from explode()/implode()/array_shift():
- https://blackfire.io/profiles/compare/b7785fda-415f-4176-a57e-f5e2417b46b0...712b3b08-4ccc-4a6a-ae9b-70b4ee030334/graph?settings%5Bdimension%5D=pmu&settings%5Bdisplay%5D=focused&settings%5BtabPane%5D=nodes&selected=Faker%5CProvider%5CText%3A%3AgetConsecutiveWords%3F00a7bff87618e1493437abb5cf94878a&callname=Faker%5CProvider%5CText%3A%3AgetConsecutiveWords%3F00a7bff87618e1493437abb5cf94878a
- https://blackfire.io/profiles/compare/b7785fda-415f-4176-a57e-f5e2417b46b0...712b3b08-4ccc-4a6a-ae9b-70b4ee030334/graph?settings%5Bdimension%5D=pmu&settings%5Bdisplay%5D=focused&settings%5BtabPane%5D=nodes&selected=Faker%5CProvider%5CText%3A%3AgetExplodedText%3F00a7bff87618e1493437abb5cf94878a&callname=Faker%5CProvider%5CText%3A%3AgetExplodedText%3F00a7bff87618e1493437abb5cf94878a

I hope this helps :-)

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