PHP Build PHP with Profile-Guided Optimization for 7% speed increase?

ethanpil · Oct 1, 2016

I just came across this article. Any thoughts?
PGO: Let It Go (PHP) | Intel® Software

eva2000 · Oct 1, 2016

Nice will have to see if this can be applied to Centmin Mod source compiles

This will create a binary of PHP which generates a profile. Now you need to run this version of php with some workload which is representative of the web site you are building
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this part would be hard to do when no sites are setup yet though ! but make for php recompiles

more info PHP 7 Performance Improvements May Increase if You Optimize it to Your Application using to PGO - PHP Classes

How to Benefit from PGO Performance Improvements?
The most important aspect to benefit from PGO performance improvements is that you or somebody else needs to compile it manually to optimize for the application you want to squeeze more performance.

This means that the generic compiled PHP binaries supplied by your Linux or another OS distribution may not perform as well as if when PHP is compiled profiling your application.

Very few PHP developers ever compiled PHP manually. Usually they take PHP for granted from their hosting company and that is it.

So to maximize the benefits of PGO, you need to download PHP source code and go through the usual sequence of steps using the commands: configure; make; make install.

However to benefit from PGO you need to change the procedure slightly. As mentioned above, you will need to compile PHP twice. In the first time you need to replace the first make command by make prof-gen. Then you run your target application that you want to optimize, and repeat the make command this time using make prof-use.

The resulting executable binaries from the last make install command is the optimized version of PHP for your application.
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ethanpil · Oct 1, 2016

Yes, I think simple it would be a 3 step process.

1) Compile PHP with instrumentation.
2) Centminmod server admin will access the websites pages and use common functions of the site to build profile.
3) Recompile php using the generated profile

I also think if we have many wordpress sites it would be good to automate the entire process.

1) Install a test domain with basic wordpress
2) Compile PHP with instrumentation.
3) use curl to access front and backend pages of test domain
4) Recompile php using the generated profile
5) delete demo domain and DB

eva2000 · Oct 1, 2016

might be easier if i can find out if make prof-gen survives subsequent php recompiles (i.e. make clean) as i could make it so initial first time php install compile uses make prof-gen, then let users run that php version for their sites and next time they recompile (not upgrade) the same php version via centmin.sh menu option 5, use make prof-use so it would be optimised for all sorts of already php requests/processing done.

Will see

eva2000 · Oct 1, 2016

more at High Performance PHP 7 | Intel® Software and interesting

First of all, let's see if we can get the compiler to generate better code.

As gcc compiles the PHP interpreter, it employs a number of heuristics to suss out how the code is going to run. This enables the compiler to generate code so that the processors will likely predict the correct branches to take. Unfortunately, these heuristics can only go so far. What the compiler really needs is an example of the PHP interpreter running, so that it is more certain of which branches will actually be taken.

To provide this example to the compiler, we employ a technique called "Profile Guided Optimization" or PGO. Using PGO, we can train the compiler by creating an instrumented version of PHP, and letting it run for a while, generating a profile. We then take this profile and recompile the PHP interpreter. The resulting compiled binary of PHP will be tuned for how it is actually used in practice.

In my talk I actually showed a demo of this: PHP 7 running WordPress compared against WordPress trained using PGO. The demo showed the relative performance delta on an instantaneous basis. The performance benefit was around 7%. For a real customer workload and for no code changes, this is actually an excellent improvement. (This was a great demo, thanks to Bogdan Andone for creating it!)
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You can take advantage of this as well. You should be able to get a nice boost in throughput for your PHP application if you download the PHP 7 sources, use "make prof-gen", use the resulting PHP to run your application and then recompile it using "make prof-use". The resulting PHP binary from this second compilation should be faster. If you have a repeatable and stable version of your PHP application to run with this as the only change, it should show an improvement.

In future, I would really like to have some kind of "golden profile" or super representative training workload which would allow us to include PGO training as a default part of the PHP build. We're not there yet in PHP7, but you can custom-build your own optimized PHP7 binary in the meantime.

The other key learning I passed on at the conference was to use a server processor like the Intel Xeon processor to run PHP. I gave the example of a patch created by one of our engineers, a patch to the fast_memcpy() function within the PHP interpreter. This patch enhanced the function with some of Intel's specialized SSE2 instructions.

Our engineer was only able to see a 1% performance improvement when running the patched PHP on a desktop Haswell processor. To our delight, when it was deployed on a Xeon server version of Haswell, the same PHP binary showed a 2.9% boost on WordPress and 5.9% improvement on MediaWiki.

So the other actionable step you can take is to run PHP on latest generation Xeon processor CPUs for the best improvement.

So in summary, here are some things you can do to amp up your PHP base website:

Switch to PHP 7. This is really an amazing boost in performance that it's just worth it to make the change.

Set up some disciplined lab which will let you compare PHP performance changes.

Download the PHP sources and train PHP using your lab workload.

If you want to develop more on the PHP interpreter itself, join the community and keep your eyes on our 0-day results.

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eva2000 · Oct 1, 2016

hmm doesn't seem to work for make prof-gen on PHP 5.6.26 so maybe PHP 7 only ?
Code (Text):
make prof-gen     
make: *** No rule to make target `prof-gen'.  Stop.

ethanpil · Oct 1, 2016

In the official PHP repo there is some reference to an earlier build with it.. not sure yet...

web-rmtools/php-5.5-pgo-ts.ini at master · php/web-rmtools · GitHub

eva2000 · Oct 1, 2016

will test on PHP 7 and see

found something useful GitHub - 01org/php_pgo_training_scripts
Code (Text):
* Authors:
*   Gabriel Samoila <gabriel.c.samoila@intel.com>
*   Bogdan Andone <bogdan.andone@intel.com>
INTRODUCTION
-----------
PHP PGO Training scripts were created as a representative execution
pattern for real life PHP applications like WordPress, MediaWiki or Drupal.
When executed during the training phase of a PGO (Profile Guided
Optimization) build process these scripts will provide similar statistics
as if the PGO training was performed with the real life application.
The advantage of using these scripts instead of real applications
is that they are easily portable and they don't need complex installation
steps as for real live use cases. The only one dependency is on MySQL. In
consequencei, the scripts can be easily integrated directly in source
ditribution packages of Zend PHP or HHVM in order to offer transparent
support for PGO builds.
The current version tries to reproduce Wordpress execution behavior.
Tested for PGO builds of PHP7 using GCC 5.0, it delivered half of the
performance speedups obtained during PGO builds trained with the real
applications. It was tested for:
- Wordpress 4.2.2: ~3.5% speedup
- Drupal 7.36: ~2% speedup
- MediaWiki 1.23.9: ~1.5% speedup

PREREQUISITES
-------------
PHP PGO Training Scripts assume you want to build optimized PHP/HHVM
binaries from scratch following the Profile Guided Optimization build process.
Here is the list of prerequisites:
- prerequisites of building PHP7/HHVM binaries from scratch (see build
documentation on PHP7/HHVM for more details)
- a C/C++ compiler supporting profile guided optimized builds. We used GCC 5.0
- a MySQL server installed, if database operations are targeted for training
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seems to suggest PHP 7 only !

eva2000 · Oct 1, 2016

@ethanpil ta-da ! Added Profile Guided Optimizations To Boost PHP 7 Performance | Centmin Mod Community

ethanpil · Oct 1, 2016

I don't see in your guide how to differentiate between first and second compile. Also how can we recompile after significant changes to PHP codebase?

eva2000 · Oct 1, 2016

ethanpil said: ↑

I don't see in your guide how to differentiate between first and second compile. Also how can we recompile after significant changes to PHP codebase?
Click to expand...

It's all done in the same centmin.sh menu option 5 php recompile run for 1st and 2nd compilations using Intel provided training profiles for wordpress, drupal and mediawiki like PHP execution patterns GitHub - 01org/php_pgo_training_scripts

eva2000 · Oct 1, 2016

I guess I could add options for users define additional php script paths to call against too. Or do it automatically just for the web root of each nginx vhost i.e. /home/nginx/domains/domain.com/public/index.php if index.php exists

ethanpil · Oct 1, 2016

FYI, if you look at the notes for the training profiles, they said its not as good as actual real world training.

it delivered half of the performance speedups obtained during PGO builds trained with the real applications
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eva2000 · Oct 1, 2016

Hmmm. Seems from reading though it's better to use Intel provided PGO training scripts if you have more than one PHP web application on server that directing php to train against just Wordpress If you only had Wordpress and no other PHP scripts, then training aginst real Wordpress path would be optimal.

ethanpil · Oct 1, 2016

Should be an option to self train or not. For example, my servers 90% wordpress. Would prefer to squeeze an extra 3-4%!

eva2000 · Oct 1, 2016

we'll see

eva2000 · Oct 1, 2016

@ethanpil more performance if you have the right cpus Beta Branch - PHP Compiler optimization for Intel Specific Processors in 123.09beta01 | Centmin Mod Community

eva2000 · Oct 1, 2016

@ethanpil added support to define your own path to your PHP web app's index.php page for PGO training Beta Branch - update inc/php_upgrade.inc add PHPPGO_INDEXPATH variable support in 1… | Centmin Mod Community

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