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HipHop : High-Performance PHP Ali-Reza Adl-Tabatabai HipHop Team Facebook. Facebook: Move fast & build things. PHP. General-purpose scripting language tailored for web development Interactive Weakly typed & dynamic.
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HipHop: High-Performance PHPAli-Reza Adl-TabatabaiHipHop TeamFacebook
Facebook: Move fast & build things
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PHP• General-purpose scripting language tailored for web
development• Interactive• Weakly typed & dynamic
<?phpvar_dump(6 + 7);var_dump('6' + '7');var_dump('six' + 'seven');var_dump((1<<63) + 0);var_dump((1<<63) + (1<<63));
int(13)int(13)int(0)int(-9223372036854775808)float(-1.844674407371E+19)
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PHP
function foo($x) {echo “foo: “. $x. ”\n”;
}foo(“hello”); // prints “foo: hello”foo(10); // prints “foo: 10”
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• General-purpose scripting language tailored for web development
• Interactive• Weakly typed & dynamic
PHP
if (...) { class B { ... }} else { class B { ... }}class C extends B { ... }
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• General-purpose scripting language tailored for web development
• Interactive• Weakly typed & dynamic
PHP
$a = ‘f’;$b = ‘c’;$c = ‘oo’;$func = $a . $ $b;$func();
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• General-purpose scripting language tailored for web development
• Interactive• Weakly typed & dynamic
PHP
class C {public $declProp = 1;
}$obj = new C;$obj->dynProp = 2; // This is OK!echo $obj->declProp . “\n”; // prints “1”echo $obj->dynProp . “\n” // prints “2”
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• General-purpose scripting language tailored for web development
• Interactive• Weakly typed & dynamic
PHP
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• General-purpose scripting language tailored for web development
• Interactive• Weakly typed & dynamic
if (function_exists(‘foo’)) { ...} if (class_exists($c)) { ...}
Memory management
• PHP is reference counted• Precise destruction semantics
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class C {function __destruct() { echo “bye!”;
}}$x = new C;$x = 1; // prints “bye!”
Concurrency
• Single-threaded programming model• Multiple requests run in parallel• No shared memory, synchronization, or direct
communication
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Performance...
C++ Java C# Ocaml PHP Ruby Python0
5
10
15
20
25
30
35
40
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CPU Time
Source: http://shootout.alioth.debian.org/u64q/benchmark.php?test=all&lang=all12
Implications for Facebook
1. Bad performance can limit user features2. Poor efficiency requires lots of re$ource$
INTERNET
webservers
storage
. . .
. . .
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What have we done?
Apache
Facebook (PHP)
PHP/Zend Facebook(binary)
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HipHop compilation flow
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Facebook(PHP)
hphpc Facebook(C++)
PHP Runtime
Webserver
Gcc
Facebook(binary)
HipHop compiler (hphpc)
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PHP AST
Optimize, Infer Types
Parser
C++
C++ Code Generator
Variant
Double
Integer
Boolean
String Array Object
Representing PHP data
type data
KindOfString
& “Lorem ipsum.”
KindOfInt 13
Type inference: fewer tags!
data
& “Lorem ipsum.”
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type
Basic operations
$a + $b
Basic operations: type dispatch
$a + $b
switch (a->m_type) { case KindOfInt: switch (b->m_type) { … } case KindOfArray: switch (b->m_type) { … } … } …}
$a + $b
Type inference: avoiding dispatch
$a + $b given$a :: Int,$b :: Int
add %rcx, %rdx
HipHop compiler: performance
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C++ Java C# Ocaml PHP Ruby Python0
5
10
15
20
25
30
35
40
45
CPU Time
Disclaimer: estimated based on running Facebook
HipHop compiler: pros & cons
• Good for production servers • Inadequate for development – Solution: the HipHop interpreter (hphpi)
• Leverages HipHop runtime & webserver
• Open problem:
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Can we get the best of both
worlds?hphpi ≠ hphpc
HipHop Virtual Machine (hhvm)
• Ambitious goal: replace both the HipHop Interpreter and Compiler
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PHP AST
Optimize, Infer Types
Parser
HHBC
Bytecode Generator
HHVM Interpreter
HHVM JIT
HipHop bytecode (hhbc)
• In-house design• Stack-base VM• Closer to PHP than
machine code
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function lookup($cache, $key) { if (isset($cache[$key])) { echo “Hit! “ . $cache[$key]; return true; } else { echo “Miss!”; return false; }}
96: Loc 0101: Loc 1106: IssetM <H E>113: JmpZ 32
118: String “Hit! “123: Loc 0128: Loc 1133: CGetM <H E>140: Concat141: Print142: PopC
143: True144: RetC
145: String “Miss!”150: Print151: PopC
152: False153: RetC
Hhvm JIT
• Beyond static type inference: dynamic type specialization1. Observe types2. Generate specialized code3. Guards to check types
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$n = 3 * $n + 1;224: Loc 0229: Int 3238: Loc 0243: CGetH244: Mul245: Int 1254: Add255: SetH256: PopC
;; Typecheck: int($n)?cmpl $4, -4(%rbp)jne __retranslate
;; Type-spec xlationmov $3, %r12dmov -16(%rbp), %r13mov %r13, %r14imul %r14, %r12add $1, %r12mov %r12, %r13mov $0x40000000, %r8mov %r8, -8(%rbp)mov %r13, -16(%rbp)
Translation cache: Reuse & specialization
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;; Typecheck: INT($n)?cmpl $4, -4(%rbp)jne __retranslate
;; Type-spec INT;; translation. . .
Translation Cache
T1:
Translator. . .
__retranslate:. . .
;; Typecheck: DOUBLE($n)?cmpl $8, -4(%rbp)jne __retranslate
;; Type-spec DOUBLE;; translation. . .
T2:
T2
$n = 1.5;...$n = 3 * $n + 1;
Current state
• hhpc– Runs www.facebook.com– Paper to appear in SPLASH ‘12
• hhvm– www.facebook.com works– Developers using it– ~27% slower than hphpc
• Download from github: https://github.com/facebook/hiphop-php/
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Perf progress
6/11-7/14
Ongoing & future work
• Performance– Profile-guided, SSA-based 2nd gear JIT– Type prediction– Tuning for the HW– Array shapes: turn hash tables into structs
• Tracing garbage collection– Copy-on-write arrays– Precise destruction semantics
• Language extensions
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Summary
• PHP enables us to move fast• Performance suffers because of interpreter• Hiphop compiler– Compiles PHP to C++ offline– Significantly improves user experience & data center
efficiency• HipHop virtual machine– A new language VM tailored to PHP– Brings dynamic JIT compilation & optimization to PHP
• Both open sourced on github
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Thanks!
Questions?
