Hi,
2010/3/24 Zeev Suraski <z...@zend.com>:
> 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.wikipedia.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
Can't we have one patch by idea?
They all seems great.
However I would like to know which one increase the performance the
most given a specific application.
I will try to find some spare time to test it against eZ Publish and
will publish my result.
A small note: I think some new macros could be introduced in the style of:
#define LITKEY_D const zend_literal *key
#define LITKEY_DC , LITKEY_D
#define LITKEY_C key
#define LITKEY_CC , LITKEY_C
#define INTERNED_FREE(s) \
if (!IS_INTERNED((s))) { efree((s)); }
Could make things easier.
Regards,
--
Patrick
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