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Bug #69885 (unexpecteadly) Increasing wasted memory when file are removed
Submitted: 2015-06-19 15:13 UTC Modified: -
Votes:3
Avg. Score:4.7 ± 0.5
Reproduced:3 of 3 (100.0%)
Same Version:2 (66.7%)
Same OS:0 (0.0%)
From: maxence at typhon dot com Assigned:
Status: Open Package: opcache
PHP Version: 5.6.10 OS: Debian 7
Private report: No CVE-ID: None
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 [2015-06-19 15:13 UTC] maxence at typhon dot com
Description:
------------
PHP 5.6.10 from tarbal, compiled with :

./configure --disable-all --prefix=/usr/local/php-5.6.10 --enable-fpm --enable-ctype --enable-mbstring --enable-gd-native-ttf --enable-zip --with-mcrypt --with-openssl --with-gd --with-jpeg-dir=/usr/lib --with-freetype-dir --with-curl --with-pcre-regex --with-gettext --enable-pdo --with-pdo-mysql=mysqlnd --with-iconv --enable-fileinfo --enable-filter --enable-json --enable-session --enable-hash --enable-libxml --enable-dom --enable-libxml --enable-simplexml --enable-bcmath --enable-soap --enable-opcache --enable-ftp --enable-intl

opcache config is :

opcache.blacklist_filename => no value => no value
opcache.consistency_checks => 0 => 0
opcache.dups_fix => Off => Off
opcache.enable => On => On
opcache.enable_cli => Off => Off
opcache.enable_file_override => Off => Off
opcache.error_log => no value => no value
opcache.fast_shutdown => 1 => 1
opcache.file_update_protection => 2 => 2
opcache.force_restart_timeout => 180 => 180
opcache.inherited_hack => On => On
opcache.interned_strings_buffer => 16 => 16
opcache.load_comments => 1 => 1
opcache.log_verbosity_level => 4 => 4
opcache.max_accelerated_files => 30000 => 30000
opcache.max_file_size => 0 => 0
opcache.max_wasted_percentage => 5 => 5
opcache.memory_consumption => 1024 => 1024
opcache.optimization_level => 0xFFFFFFFF => 0xFFFFFFFF
opcache.preferred_memory_model => no value => no value
opcache.protect_memory => 0 => 0
opcache.restrict_api => no value => no value
opcache.revalidate_freq => 2 => 2
opcache.revalidate_path => Off => Off
opcache.save_comments => 1 => 1
opcache.use_cwd => On => On
opcache.validate_timestamps => On => On

We used to remove a lot of php files from time to time (~ 70Mb) when releasing, without any manual opcache flush or php restart. Every time we remove the files, the same amount of space is added to wasted_memory. Looks like opcache does not reclaim the memory when the file is removed (and then recreated) but only put it as "wasted". Also, the memory wasted is far bigger than the configured 5%, and opcache doesn't restart.

I achieved to reproduce this in a simple test (see below). Note that the sleep time matters. With "sleep 3", the wasted memory increase after every cycle. With "sleep 2", it only increases every ~ 2 times, which let me think the issue has something to do with the revalidate process (and revalidate_freq).




Test script:
---------------
 # for i in $(seq 1 100);do rm -f /var/www/web-default/a.php && echo '<? echo("hi"); ?>' > /var/www/web-default/a.php; sleep 3; curl -s http://127.0.0.1/a.php >/dev/null; curl -s http://127.0.0.1/opcache_stat.php |grep wasted_memory;done
       

Expected result:
----------------
wasted memory should not increase, so something like :

 "wasted_memory": 72192,
 "wasted_memory": 72192,
 "wasted_memory": 72192,
 "wasted_memory": 72192,

Actual result:
--------------
wasted memory increase for the same size every time.

"wasted_memory": 72192,
"wasted_memory": 72960,
"wasted_memory": 73728,
"wasted_memory": 74496,
"wasted_memory": 75264

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