Re: Reducing load for LAMP app?

Jerry Stuckle wrote:
Jeremy wrote:
Gilles Ganault wrote:
Hello,

I'm no LAMP expert, and a friend of mine is running a site which is a
bit overloaded. Before upgrading, he'd like to make sure there's no
easy way to improve efficiency.

A couple of things:
- MySQL : as much as possible, he keeps query results in RAM, but
apparently, each is session-specific, which means that results can't
be shared with other users.
Is there something that can be done in that area, ie. keep the maximum
amount of MySQL data in RAM, to avoid users (both logged-on and
guests) hitting the single MySQL server again and again?

- His hoster says that Apache server is under significant load. At
this point, I don't have more details, but generally speaking, what
are the well-know ways to optimize PHP apps?

Thank you.

memcached: http://memcached.sf.net (for caching dynamic data in memory)
apc: http://us2.php.net/apc (caches script bytecode to reduce compilation overhead)

These two modules will help enormously. I guarantee it. Using apc is pretty much transparent, but memcached will require modifying your database abstraction layer using the memcached functions (http://php.net/manual/en/ref.memcache.php).


Not necessarily. MySQL and the OS both cache data - and generally do a better job at a lower cost than using memcached.


Not necessarily. Using memcached on the application layer can save a lot of network traffic to and from the database server, and can help immensely. Quite immensely. The OS doesn't cache data from a separate database server. I doubt the OP is running a local database server, as he explicitly refers to the "MySQL server".

<Snipped re: connection pooling>

WRONG, WRONG, WRONG! This INCREASES resource usage on the server. With persistent connections, you must have the maximum number of connections *ever* required allocated *all of the time* - even if no one is using your server.

MySQL persistent connections should not be used except in extreme cases - like when you're running 100+ connections per second.

Sorry, but have you ever done any research on this topic? Connection pooling is a well-established mechanism for boosting performance on high-traffic servers. Keeping connections open is not a significant drain on server resources, and can save a lot of overhead in creating and tearing down connections. Also, you don't really know how many connections per second his application is handling. I suggested he try it and gauge the results for himself. If it really is slower, don't do it.


The FIRST thing to do when having performance problems is to identify the cause of the performance problem.

That is certainly true.

You're making suggestions without having any idea where the hold up is.

And what would you suggest? Should I do a code review for him? Rewrite his queries? Or should I suggest a few common tweaks that might help from a configuration standpoint? Or maybe we should all just stick to flame wars instead of generating any useful discussion?

In at least two cases, your suggestions could actually HURT performance. And the third case may or may not help. If, for instance, the majority of the resource usage is spent in long MySQL queries,

People are always saying "X is the bottleneck, so improving Y won't help." This is just not true. It won't help as much as improving X, but every cycle saved on redundantly compiling PHP code is a cycle that can be used doing useful computation. NOT running a bytecode cache is pretty pointless. Why not do it?

Jeremy

.

Relevant Pages

  • Re: Experiences with mysql_pconnect?
    ... talk to a MySQL 5.0.45 DB on an Apache 1.3 series server. ... dangling connections to the server at the php.net site. ... especially when the server is remote as it requires multiple calls to MySQL. ... queries that you execute on a regular basis, preparing it and then ...
    (comp.lang.php)
  • Re: Experiences with mysql_pconnect?
    ... talk to a MySQL 5.0.45 DB on an Apache 1.3 series server. ... dangling connections to the server at the php.net site. ... > Using prepared statements will probably speed up your app a lot. ... especially when the server is remote as it requires multiple calls to MySQL. ...
    (comp.lang.php)
  • Re: Free database bindings for Windows?
    ... server from an Ada application. ... I might be able to run the database server on a Linux ... My intention is to use either PostgreSQL or MySQL. ... There is an ADBI (Ada Database Interface) project on ...
    (comp.lang.ada)
  • Re: Reducing load for LAMP app?
    ... MySQL: as much as possible, he keeps query results in RAM, but ... His hoster says that Apache server is under significant load. ... Using apc is pretty much transparent, but memcached will require modifying your database abstraction layer using the memcached functions. ... With persistent connections, you must have the maximum number of connections *ever* required allocated *all of the time* - even if no one is using your server. ...
    (comp.lang.php)
  • Re: SBS 2003 IIS BASED SERVICES FAIL INTERMITTENTLY
    ... If I read your post correctly, you have a switch where the SBS ... Run DHCP server on your SBS, and set all client machine nics to dynamic. ... Once you have your nics configured, run the Connect to the Internet wizard, ... QUESTION1 - what is REFUSING CONNECTIONS? ...
    (microsoft.public.windows.server.sbs)