1. Hacking HHVM
Waqar Alamgir
@wajrcs walamgir@folio3.com
Aug 13, 2015

2. “What is HHVM?”

3. HHVM is not a source code transformer
That was HPHPc, it’s dead.
▪ Runs your PHP pages live,
just like PHP
▪ Uses a builtin web server
or FastCGI – Runs anywhere
(on 64-bit x86 linux)
▪ Drop-in replacement for PHP
(mostly)
Webserver
(apache, nginx, etc…)
Database
(mysql, posges,
mongo, redis, etc…)
cart.phphome.phplogin.php
index.php
PHP
A
P
C

4. HHVM is not a source code transformer
That was HPHPc, it’s dead.
▪ Runs your PHP pages live,
just like PHP
▪ Uses a builtin web server
or FastCGI – Runs anywhere
(on 64-bit x86 linux)
▪ Drop-in replacement for PHP
(mostly)
Webserver
(apache, nginx, etc…)
Database
(mysql, posges,
mongo, redis, etc…)
cart.phphome.phplogin.php
index.php
HHVM
Just Plug and Pray!
Erm, I mean… Play

5. HHVM supports (most) PHP syntax
Tracking HEAD
▪ Pending: Splat (5.6)
(Variadics work already)
▪ Finally
▪ Generators
▪ Namespaces
And some of its own
▪ Scalar type hint
(and much much more)
▪ Async co-routines
▪ Generics
▪ Collections (smart arrays)
▪ XHP (Integrated XHTML)
▪ User Attributes

6. HHVM’s Parity Gap
• Only about 60% of PHP’s unit tests pass.
• 20 top framework (and more) do pass.
• So I wouldn’t sweat the small stuff.

7. HHVM is easy to install
If you’re on Ubuntu
▪ deb http://dl.hhvm.com/ubuntu saucy main
▪ apt-get update
▪ apt-get install hhvm (or hhvm-nightly)
▪ Provides one binary covering cli, fcgi server, and libevent server
▪ Coming very soon to a Debian near you!
Or something Debianish…

8. HHVM is buildable
On other linux distros (MacOSX in interp mode only)
• http://hhvm.com/repo/wiki
• gcc 4.8 or later (soon to be 4.8 or later)
• Boost 1.49 or later
• Lots of other dependencies….
• git clone git@github.com:facebook/hhvm
cmake .
make –j
• hphp/hhvm/hhvm
xkcd.org/303

9. Running a server
Built-in HTTP server FastCGI
Server {
Port = 80
Type = libevent
SourceRoot = /var/www
}
Log {
Level = Error
UseLogFile = true
File = /var/log/hhvm-error.log
Access { * {
File = /var/log/hhvm-access.log
Format = %h %l %u %t ”%r” %>s %b
}}
}
VirtualHost {
…}
StaticFile {
…}
Server {
Port = 9000
Type = fastcgi
SourceRoot = /var/www
}
Log {
Level = Error
UseLogFile = true
File = /var/log/hhvm-error.log
Access { * {
File = /var/log/hhvm-access.log
Format = %h %l %u %t ”%r” %>s %b
}}
}
Requires patched libevent

10. Running a FastCGI server
nginx HHVM
server {
server_name www.example.com;
root /var/www;
index index.php;
location ~ .php$ {
fastcgi_pass unix:/var/run/hhvm.sock
fastcgi_index index.php;
fastcgi_param SCRIPT_FILENAME
/var/www$fastcgi_script_name;
include fastcgi_param;
}
}
Server {
FileSocket = /var/run/hhvm.sock
Type = fastcgi
SourceRoot = /var/www
}
Log {
Level = Error
UseLogFile = true
File = /var/log/hhvm-error.log
Access { * {
File = /var/log/hhvm-access.log
Format = %h %l %u %t ”%r” %>s %b
}}
}

11. HPHPC in 2010 - 2011
• Crazy cross compiler.
• Converts php to C++.
HHVM in 2013
• Complete new VM.
• Facebook is running it on Production.
• Great community, over 750 pull requests.

12. PHP is webscale
HHVM’s JIT is the secret sauce

13. HHVM – Bytecode interpreter
• PHP5 style bytecode execution
• APC-like caching of bytecodes
• Perf about on par with PHP
Modified?
Invalidate
Cache
Compile to
Bytecode
Run
Bytecode
Y
N

14. HHVM – Native code JIT
• Bytecodes run a few times “cold”
• Variable type inference
• Hotpath detection
• Transform to native code
Modified?
Invalidate
Cache
Compile to
Bytecode
Have native?
Run Native
Hot?
Run
Bytecode
Compile to
Native
Y
Y
Y
N
N
N

15. HHVM – Compiling to Native

16. HHVM – Repo Authoritative Mode
• “Production Mode”
• Improved offline pre-analysis
• Assumes no changes
• Another 10% or so perf gain
PreCompil
e Bytecode
Have native?
Run Native
Hot?
Run
Bytecode
Compile to
Native
Y
Y
N
N

17. HHVM – Warming Up Server

18. Your CPU on PHP.

23. Magento (Daniel Sloof)
https://t.co/UB1aOzJ73c

24. Magento (Daniel Sloof)
https://t.co/UB1aOzJ73c

25. Symfony
(Christian Stocker)
Requests per Second
http://bit.ly/1fCRw99

26. Symfony
(Christian Stocker)
Page load Time
http://bit.ly/1fCRw99

27. HPHPd – HPHP Debugger
• Interactive shell
• GDB-like debugging
• Standalone or w/ server
• Breakpoints
• Watches
• Macros

28. Extending HHVM
You *can* do that in PHP

29. Writing a PHP Extension…
zend_bool array_column_param_helper(zval **param,
const char *name TSRMLS_DC) {
switch (Z_TYPE_PP(param)) {
case IS_DOUBLE: convert_to_long_ex(param);
case IS_LONG: return 1;
case IS_OBJECT: convert_to_string_ex(param);
case IS_STRING: return 1;
default: php_error_docref(NULL TSRMLS_CC, E_WARNING, "The %s key should be either a string or an integer", name);
return 0;
}
}
PHP_FUNCTION(array_column) {
zval **zcolumn = NULL, **zkey = NULL, **data;
HashTable *arr_hash;
HashPosition pointer;
if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "hZ!|Z!", &arr_hash, &zcolumn, &zkey) == FAILURE) { return; }
if ((zcolumn && !array_column_param_helper(zcolumn, "column" TSRMLS_CC)) ||
(zkey && !array_column_param_helper(zkey, "index" TSRMLS_CC))) {
RETURN_FALSE;
}
array_init(return_value);
for (zend_hash_internal_pointer_reset_ex(arr_hash, &pointer);
zend_hash_get_current_data_ex(arr_hash, (void**)&data, &pointer) == SUCCESS;
zend_hash_move_forward_ex(arr_hash, &pointer)) {
zval **zcolval, **zkeyval = NULL;
HashTable *ht;
if (Z_TYPE_PP(data) != IS_ARRAY) { continue; }
ht = Z_ARRVAL_PP(data);
if (!zcolumn) { zcolval = data; }
else if ((Z_TYPE_PP(zcolumn) == IS_STRING) &&
(zend_hash_find(ht, Z_STRVAL_PP(zcolumn), Z_STRLEN_PP(zcolumn) + 1, (void**)&zcolval) == FAILURE)) { continue; }
else if ((Z_TYPE_PP(zcolumn) == IS_LONG) &&
(zend_hash_index_find(ht, Z_LVAL_PP(zcolumn), (void**)&zcolval) == FAILURE)) { continue; }
if (zkey && (Z_TYPE_PP(zkey) == IS_STRING)) { zend_hash_find(ht, Z_STRVAL_PP(zkey), Z_STRLEN_PP(zkey) + 1, (void**)&zkeyval); }
else if (zkey && (Z_TYPE_PP(zkey) == IS_LONG)) { zend_hash_index_find(ht, Z_LVAL_PP(zkey), (void**)&zkeyval); }
Z_ADDREF_PP(zcolval);
if (zkeyval && Z_TYPE_PP(zkeyval) == IS_STRING) { add_assoc_zval(return_value, Z_STRVAL_PP(zkeyval), *zcolval); }
else if (zkeyval && Z_TYPE_PP(zkeyval) == IS_LONG) { add_index_zval(return_value, Z_LVAL_PP(zkeyval), *zcolval); }
else if (zkeyval && Z_TYPE_PP(zkeyval) == IS_OBJECT) {
SEPARATE_ZVAL(zkeyval);
convert_to_string(*zkeyval);
add_assoc_zval(return_value, Z_STRVAL_PP(zkeyval), *zcolval);
} else {
add_next_index_zval(return_value, *zcolval);
}
}
}

30. The same function in HHVM
<?php
function array_column(array $arr, $col, $key = null) {
$ret = [];
foreach($arr as $key => $val) {
if (!is_array($val)) continue;
$cval = ($col === null) ? $val : $val[$col];
if ($key === null || !isset($val[$key])) {
$ret[] = $cval;
} else {
$ret[$val[$key]] = $cval;
}
}
return $ret;
}

31. Crossing the PHP->C++ barrier
Array HHVM_FUNCTION(array_column, CArrRef arr, CVarRef col, CVarRef key) {
Array ret;
for (auto &pair : arr) {
Variant key = pair.first, val = pair.second;
if (val.isArray()) continue;
Array aval = val.toArray();
Variant cval = col.isNull() ? aval : aval[col];
if (key.isNull() || !aval.exists(key)) {
ret.append(cval);
} else {
ret[aval[key]] = cval;
}
}
return ret;
}

32. Questions

33. Resources
• http://hhvm.com/repo
• http://hhvm.com/blog
• http://hhvm.com/twitter
• http://docs.hhvm.com
• hphp/doc in git repository for Options and Technical… Stuff
• Freenode / #hhvm
• http://hhvm.com/fb/page
• http://hhvm.com/fb/general
• @HipHopVM
• @HackLang