HHVM Tuning

• Disabling The Typechecker:

HHVM automatically runs the typechecker - this is useful in development, but assuming you have it running in your development workflow and in your CI system, there is not much additional benefit to running it in production, and the increased memory usage can be costly in production. To disable it, add the following to /etc/hhvm/server.ini:

hhvm.hack.lang.auto_typecheck=0
hhvm.hack.lang.look_for_typechecker=0

Reference:
https://hub.docker.com/r/hhvm/hhvm-proxygen/

• Switch to UNIX socket inside of port for fastcgi mode:

HHVM is considered for environments under heavy load so the first configuration change you can do is to make HHVM listen to a socket instead of a TCP port. Thus, the communication between Nginx and HHVM will require less CPU and memory.

Add this to: /etc/hhvm/server.ini

hhvm.server.file_socket=/var/run/hhvm/hhvm.sock
; hhvm.server.port = 9000

I also common out the port line to increase a bit of security.

Then change the Nginx config to hhvm as well:
/etc/nginx/hhvm.conf

fastcgi_pass unix:/var/run/hhvm/hhvm.sock;

• Tweaking Memory:

By default the memory_limit is equal to 17179869184 bytes, which is 16 GB.
Such a high memory resource limit will certainly kill a server with a few GB of RAM, making it unresponsive.
I decrease this value to 500 MB for a 1 GB memory Server:

Add this to: /etc/hhvm/php.ini

memory_limit = 500M

Restart to apply the changes:

service hhvm restart
service nginx restart

Reference:
https://www.digitalocean.com/community/tutorials/how-to-install-hhvm-with-nginx-on-ubuntu-14-04

• A much more pushed example for a bigger server:

; php options
pid = /var/run/hhvm/hhvm.pid

; hhvm specific
; hhvm.server.port = 9000
hhvm.server.file_socket= /var/run/hhvm/hhvm.sock
hhvm.server.type = fastcgi
hhvm.server.default_document = index.php

; logging settings
hhvm.log.use_log_file = true
hhvm.log.file = /var/log/hhvm/error.log
hhvm.log.header = true
hhvm.log.level = Warning
hhvm.log.always_log_unhandled_exceptions = true
hhvm.log.runtime_error_reporting_level = 8191

hhvm.mysql.typed_results = false
hhvm.repo.central.path = /var/run/hhvm/hhvm.hhbc
hhvm.server.source_root = /var/www/html

; php compatibility
hhvm.server.allow_duplicate_cookies = 0
hhvm.enable_obj_destruct_call = 1
hhvm.enable_zend_sorting = 1
hhvm.enable_zend_compat = 1

; logging
hhvm.log.admin_log.file = /var/log/hhvm/admin.log

; admin server

hhvm.admin_server.password = xxx

hhvm.admin_server.port = 8088
hhvm.admin_server.thread_count = 1

; required for magento2
hhvm.libxml.ext_entity_whitelist = "file"

; apc
hhvm.server.apc.enable_apc = true

; jit
hhvm.jit = true
hhvm.jit_warmup_requests = 5

; debugger
hhvm.debugger.enable_debugger = false
hhvm.debugger.enable_debugger_server = false
hhvm.debugger.default_sandbox_path = /var/www/html


hhvm.enable_zend_ini_compat = false

 hhvm.jit_a_cold_size=201326592
 hhvm.jit_a_frozen_size=201326592
 hhvm.jit_a_size=201326592
 hhvm.jit_global_data_size=201326592
 hhvm.mysql.connect_timeout=6000
 hhvm.repo.central.file_group=www-data
 hhvm.repo.central.file_user=www-data
 hhvm.server.connection_timeout_seconds=300
 hhvm.server.implicit_flush=1
 hhvm.server.request_timeout_seconds=300
 hhvm.server.thread_count=10000

Reference:
https://github.com/facebook/hhvm/issues/7754