Performance Questions

Anon

Will it help in terms of performance if I place each function in a separate file, and manually include the files that I need?

It seems to me that this method will prevent the parser from parsing unnecessary code that will never be executed, thus improving performance.

Or is this much ado about nothing? Insignificant to performance and only create a big mess of files to manage?
Thanks,

Tom

junebug

put this at the start of your script:

$start = microtime();

and this at the end:

$end = microtime();

parse your script and subtract the top number from the bottom. that will give you the time it took to execute. try it both ways and see which gives you the faster time.

Anon

I guess the best way is to experiment. And that is easily done for small scripts, i might sound lazy here, but for large scripts, this could be very time consuming to convert your code to a different format... are there any better ways? Does PHP cache any of the code after parsing and interpreting, or does it reparse the entire script each time it is executed?

[deleted]

There's been a discussion about this some time ago.

Splitting things up reduces the amount of code per script, but including more scripts takes time. Sometimes it takes more time to include the scripts than to parse them.

There's another BIG thing: maintenance.
Can you maintain your code when it's devided into 34 small scripts?

Anon

As another respondee posted, put in some timing code an experiment, but the results are that are that parsing is very expensive, whereas including one file vs. 10 or 20 files makes a negligable difference. The advantage of some logical splitting is that you can decide what to include when, and this can make a big difference.

A logical split can also make maintainance easier than one huge file. You can focus quicker on the bit that you're thinking working on, will have less other code to scroll past, and so on.

But the 'best' and easiest all round is to use a cache like the APC cache, or the PHP Accelerator (www.php-accelerator.co.uk). The latter is my offering. Caches keep the compiled code, eliminating repeated parsing, and mean that you don't have to make the code messy with conditional includes, and potentially waste time on designing just in order to do conditional including.

[deleted]

"but the results are that are that parsing is very expensive, whereas including one file vs. 10 or 20 files makes a negligable difference."

In my experience it's the including that's more expensive.

I'd benchmark it a few times because it depends VERY much on how much code you can exclude.
Also remember, include() is a filesystem operation, so if your filesystem is busy, you'll have to wait...

Anon

Vincent,

Yes you're right of course. Even with a cache like mine that eliminates reading of files, and even most memory copying and allocation operations prior to executing scripts, you're still going to be even faster if you simply cut out chunks of code. I do this extensively on a site, and it of course makes a difference. Combined with transparent caching of static query results and on the fly generation and caching of more optimal page rendering code, it makes a big difference :-)

If you're hitting the disc to read your source then of course there's a chance for I/O contention with whatever else is going on - another good reason to use a cache btw.

This is why you should:

1) use good quality and fast RPM drives

2) ensure that UDMA is turned on with hdparm (make sure you have UDMA drives first please ;-). On most linuxes it isn't by default, and people never even realise that their lovely fast UDMA discs are giving them about 3MB/sec performance instead of well over 30MB/sec that they should be getting!
Why not try hdparm -t -T /dev/hda today and see what you get. Anything less than around 25MB and you're I/O performance needs help. (160MB/35.5MB mem/disc performance or even better is attainable)

3) Do the best thing you can do for any machine - give it some more RAM. Running with 128, then go up to 256. Got 256, why not go to 512. Your box can probably handle 1 to 1.5G Ram, and even fast ECC ram is pretty cheap. Time spent on trying to tweak scripts and then on fixing what you broke in the process is not.

Nick