php, opcache and linux huge pages

General Tech Bugs & Fixes 2 years ago

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Posted on 16 Aug 2022, this text provides information on Bugs & Fixes related to General Tech. Please note that while accuracy is prioritized, the data presented might not be entirely correct or up-to-date. This information is offered for general knowledge and informational purposes only, and should not be considered as a substitute for professional advice.

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manpreet Tuteehub forum best answer Best Answer 2 years ago

 

I'm using php-fpm configured to use file cache like this (php.ini):

opcache.enable=1
opcache.file_cache=/var/lib/hugetlbfs/group/www-data/pagesize-2MB
opcache.huge_code_pages=1

and by using debug.php:

This is normal HTML

But the following table is generated by PHP:

I can see that Zend OPcache is up and running, the opcache is enabled and using my configuration; also opcache-gui is showing the memory being used. When I'm checking /var/lib/hugetlbfs/group/www-data/pagesize-2MB I discover that contains no file (sudo find /var/lib/hugetlbfs/group/www-data/pagesize-2MB -type f) and has 0 size (sudo du -sh /var/lib/hugetlbfs/group/www-data/pagesize-2MB); this also happens even while my php website is continuously stressed with requests. I do find though many directories (e.g. /var/lib/hugetlbfs/group/www-data/pagesize-2MB/0c5f279af5b0301d11f2fde4c3271f7d/.../php-pages/wordpress/wp-content) while also the huge code memory seems to be used:

grep Huge /proc/meminfo
AnonHugePages:     14336 kB
ShmemHugePages:        0 kB
HugePages_Total:      33
HugePages_Free:       18
HugePages_Rsvd:       18
HugePages_Surp:        1
Hugepagesize:       2048 kB

Q: shouldn't that pagesize-2MB directory contain some cached files? If not then why not? If yes then how should I fix this missing cached files?


PS: my configuration is below

  • Ubuntu 16.04.5 LTS
  • PHP 7.0.32-0ubuntu0.16.04.1
  • using /usr/sbin/php-fpm7.0

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