Hi Jared,
Jared Williams wrote:
Hi
Wondering if there is any plans to for new serialization
method?
Not in this patch.
One of the things that igbinary does is store strings only
once, and now that the engine supports string interning natively,
seems that serialization and deserialization could benefit.
Though I guess igbinary could be patched to take advantage of
string interning?
Probably it can. However, I've never looked into it, so I can't be sure.
Thanks. Dmitry.
-Jared
-----Original Message-----
From: Dmitry Stogov [mailto:dmi...@zend.com]
Sent: 13 April 2010 14:53
To: internals@lists.php.net
Subject: [PHP-DEV] [RFC] Performance improvements
Hi,
I've published all the patches, their description and
performance evaluation at
http://wiki.php.net/rfc/performanceimprovements
In two words the patches give 0-20% improvement even on
real-life applications.
I'm going to commit them into trunk in a week in case of no
objections.
Of course, they are binary incompatible. Some extensions
(especially VM depended e.g. APC, xdebug, etc) will have to
be modified to support the changes.
Thanks. Dmitry.
Zeev Suraski wrote:
Hi,
Over the last few weeks we've been working on several ideas
we had for
performance enhancements. We've managed to make some good
progress.
Our initial tests show roughly 10% speed improvement on real world
apps. On pure OO code we're seeing as much as 25% improvement (!)
While this still is a work in progress (and not production quality
code
yet) we want to get feedback sooner rather than later. The diff
(available at http://bit.ly/aDPTmv) applies cleanly to
trunk. We'd be
happy for people to try it out and send comments.
What does it contain?
1) Constant operands have been moved from being embedded within
the
opcodes into a separate literal table. In additional to the zval
it
contains pre-calculated hash values for string literals. As
result PHP
uses less memory and doesn't have to recalculate hash values for
constants at run-time.
2) Lazy HashTable buckets allocation - we now only allocate the
buckets array when we actually insert data into the hash
for the first time.
This saves both memory and time as many hash tables do not have
any
data in them.
3) Interned strings (see
<http://en.wikipedia.org/wiki/String_interning>http://en.wikip
edia.org/wiki/String_interning).
Most strings known at compile-time are allocated in a
single copy with
some additional information (pre-calculated hash value,
etc.). We try
to make most incarnations of a given string point to that
same single
version, allowing us to save memory, but more importantly - run
comparisons by comparing pointers instead of comparing strings and
avoid redundant hash value calculations.
A couple of notes:
a. Not all of the strings are interned - which means that if a
pointer comparison fails, we still go through a string comparison;
But if it succeeds - it's good enough.
b. We'd need to add support for this in the bytecode
caches. We'd be
happy to work with the various bytecode cache teams to guide how
to
implement support so that you do not have to intern on each
request.
To get a better feel for what interning actually does, consider
the
following examples:
// Lookup for $arr will not calculate a hash value, and will only
require a pointer comparison in most cases // Lookup for
"foo" in $arr
will not calculate a hash value, and will only require a pointer
comparison // The string "foo" will not have to be
allocated as a key
in the Bucket // "blah" when assigned doesn't have to be
duplicated
$arr["foo"] = "blah";
$a = "b";
if ($a == "b") { // pointer comparison only
...
}
Comments welcome!
Zeev
Patch available at: http://bit.ly/aDPTmv
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