multiprocessors and PHP???

Anon

Hi,

Does anyone know whether PHP has multi processor support? I don't know a lot about running scripting languages under multiple processors; but my company is considering on investing in a Sun Server.

We want to be able to run our PHP scripts (which I know will work), but we are planning on getting 2 processors in our system. Can PHP utilize BOTH these processors somehow?

If anyone has ever ran PHP programs on a multi processor system and has found a way to utilize all processors, PLEASE let me know.

I really don't want my company to make a foolish investment in Sun servers when we can just get a really fast x86 based system.

Thanks,
-sridhar

[deleted]

In a multi-CPU environment, the OS will allways distribute it's tasks over all available CPU's.

It's a kind of internal load-balancing.

So it really doesn't matter wether PHP is single- or multi-CPU, the OS will allways give the next task to the CPU with the lowest load at that time.

The more CPU's, the fewer tasks per CPU, the faster each task gets.

BTW PHP is usually run as a module for a webserver, so if there's a multi-CPU capability problem, it's the webserver that should be multi-CPU, not PHP.

saloon12yrd

Hi,

we use a Dual Pentium III 800 as livesystem, and a otherwise identical single processor machine as developmentsystem, so I can tell you that you indeed will benefit from additional CPUs.
However the multiprocessor-ability lies not within PHP but within the Webserver (Apache in our case) and of course the OS (Linux for us).
Scripts that handle "non-distributable" problems will not be speed up, in this case you "only" have a spare CPU left for another task (handling nearly twice the number of requests without getting slower).
However most scripts will be spread among the CPUs.

Concerning Sun systems, I only know the server benchmarks and no real livedata but it seems that a dual Pentium can compete a small Sun which in our case lead to the existing systems, so you might want to do a little research there.
BTW, a single Pentium II, 256MB RAM, Linux handles half a million siteimpressions per month at normal systemload.

Hope that helps a bit,

Dominique

Anon

Vicent and Dominique,

Thanks so much for your clarification.

I understand that if I compile PHP as a module w/ Apache, it HAS to be Apache that utilizes more than 1 CPU.

Okay great! Now, my question is: Does Apache 1.3.xx (1.3.19 and 1.3.20) support MPs? I know that Apache 2.xx supports it, but since versions 2.xx is considered "beta" I really don't know whether it will be ideal for this project my company is working for.

In order to clarify why we want to use Multiple Processors, I'll explain the project. Basically, it is a portal for an ISP. This ISP has over 100000 users and we are expecting at least 10000 unique users a day (~100000 page accesses). So we are investing in a Sun Server (with 4 processors and 2 GB of memory and a RAID disk array).

We are also planning to run an e-mail system (webmail coded in PHP) on this server. Right now our budget is small so we are only investing in one server instead of a cluster or a network of servers.

So if you guys can recommend whether Apache 2.xx will be the ideal server (or perhaps another like iPlanet/Netscape enterprise) let me know.

thx
-sridhar

[deleted]

No, apache does NOT require to support multiple processors.

The OS will distribute ALL processes accross the CPUs. Apache does NOT have to do that itself.

I think you should do some serious investigations into your performance needs,
because a quad-CPU Sunsparc will cost some serious money. It may be cheaper to get two smaller machines.
Servers love memory, and a quad-CPU machine with 2GB of memory has only 512M per CPU, which is not a lot. 4GB is more like it.

What's more, if your budget is a 'problem' why not go for Intel based machines and run linux? Then you can probably get 20 high-spec machines for the same price.

Anon

Actually vincent a program must be multi-threaded to take advantage of mp, php isn't multi-threaded, Apache is, but this doesn't mean that php will use more than one processor. Yes Apache will, but all php processes started by an apache thread will be run on the processor that the apache thread was running on, however these processes usually don't take long to run. The database is usually the bottleneck, and most are multi-threaded (I know MySQL is)

moonie 😉

Anon

see my earlier statment in response to vincent

[deleted]

And that was just about exactly what I said... or apparently, what I was trying to say.

Anon

There were some serious investigations in the german CT Magazine, which have shown that you benefit from a dual machine in a relative good way when you take the investment into account but a quad system isn't thas worthy.

Anon

In a webserver environ, especially one with lots and lots of traffic, I can see there being an advantage to even a quad machine. But above and beyond that, there is the question of L2 cache efficiency. A quad celeron with no L2 cache (the early ones) would be about useless in this environment.

Of course we know that having a high speed local cache of oft used information and instructions makes a lot of sense. If each cpu in a quad or dual system had an efficient cache and way of dealing with cache misses, then your system would blaze. One thing to remember though. Just becuase there are 4 cpu's, there isn't four times the amount of information being cached. Each cpu is going to cache what it see's fit. However, all four of the cpu's will cache very similar bits of data, if not the exact same.

By the way, did CT give a scenario under wich they are making these statements. Like what usage for example?

Also, I remember an article in Byte a long time ago that DOES NOT agree with what CT has to say on the topic. It showed that as requests increased, the system load did as well. AND, systems with the ability to handle greater traffic as such have an advantage of those that don't. In this case, the 4 proc systems.

Later on,
morpheus()

[deleted]

Remember we were talking about a quad SPARC, not intel.
SPARC has been creating systems with over 1k CPU's in one machine, so I guess they have a more efficient multi-CPU environment than intel does.

saloon12yrd

Anyhow, since Sridhar stated that he needs to handle lots of small requests and not fewer big, timeconsuming scripts (like archiving, massive UPDATE/INSERT/SELECT statements, ...) I tend to believe that he'd be better off using a rather cheap dual/quad intel System than a Sparc just because of the price.
As I stated earlier a Penium II with 256Megs of RAM handles half a million PIs per Month with ease. He stated that they expect 10,000 Users per day - well thats one user every 8.6 seconds - even a single processor system should handle that but lets be on the safe side.
Suggestion: Quad Pentium III ~1GHz, 4GB RAM, System on RAID-1, Data on RAID-5.

Dominique

[deleted]

A single Sparc-400Mhz can do more than 100k pageviews per hour with simple PHP/mysql work, so I guess a Quad P3@1Ghz is ehm... a little overdone?

saloon12yrd

Hehehe yeah it for sure is, but I guess it's still cheaper than a single Sparc?
Downgrade to a dualsystem if you like but on the other hand they have the opportunity to buy a multiprocessor Sparc so money can not be that sparse... why not play safe and buy a bigger system.

Another thing to consider of course is knowledge - if there's considerable Linuxknowledge in-house I'd stick to Linux/Intel, if there already are some Admins experienced with Solaris maybe you end up cheaper buying a Sparc (due to faster install/upgrade/fix/... time).

Dominique

Anon

Wether it's a SPARC, Intel, AMD, or Alpha based system, everything that's been said about cache effeciency still applies.

Additionally, my main thrust wasn't about whose multi proc evnironment is more efficient (eventhough these days I have to say that belongs to Alpha/AMD, or is about to), but instead the efficiency of the L2 cache. This is critical! Not just the speed of the cache (wether it runs at cpu speed, or system/bus speed, or something else), or it's location (on CPU or on the board) but how well the cpu deals with a cache miss. In a pipelined CPU, the penalty of a cache miss can negatively affect it's output for 5 to 10 plus cycles depending on the CPU. Now if your CPU is averaging a higher percentage of cache misses, there is going to be a rather negative effect on performance compared to another CPU with either fewer misses, deals better with misses, or both.

It seems more like dudes' bosses have more money than knowledge in this situation and are hearing glamour names or are having smoke blown up their posteriors by greedy salesman.

For the most part, I say a dual CPU system, Intel or AMD would be fine for this application. Of course, SCSI drives would be very important in this application, as well as putting any db's on their own drives.

But then what do I know?

saloon12yrd

L2 cache issues aside (far to complicated for a gerneral "install" forum IMHO) I agree.
As said in another post I'd chose:
Quad Pentium III ~1GHz, 4GB RAM, System on RAID-1, Data on RAID-5.

Overequipped? Most likely.
Future safe? Definatelly.
Fun? Hell yeah!

Although much cheaper in CPU prices I would not stick to AMD (yet) but wait until their multiprocessor ability is a little more mature. (Check some of the recent Dual Athlon reviews for further info.)

Dominique

Anon

Oh yeah, I completely agree with you on AMD at this moment. Their multi proc tech has yet to prove itself. I was saying they are worth consideration in a single CPU application.

I'll say a good thing for Intel though. They spent a lot of time working on cache throughput on the P6 core, later PII's and the PIII in particular. It's a great performer in that area.

I think the setup you mention would kick arse and save a bundle. Maybe even get Srid a bonus :-).

Later on,
morphues()

[deleted]

Definetely not cheaper than single-sparc.

I wouldn't fork out cash for a quad P3 now that P3 is being overtaken by P4 and AMD processors. Dual AMD is already available.

I'd definately make some serious considerations about cost, performance and in-house knowhow.

Starting with an estimate of just how much CPU power you really need, because thaty is often overrated.

saloon12yrd

NOT cheaper? Hmm can you name a price? Not that I don't believe you, I'm getting curious 🙂)
AMD's multiprocessor technique ain't very mature (see reviews) yet so I'd wait a little. As for Pentium 4... too expensive yet. It even needs (again, expensive) RDRAM.
And as you said, Sridhar won't need severe numbercrunching power so I'd stick to the now-cheap Pentium III.

Dominique

[deleted]

There are IDE based servers from around $600 and up.

I agree AMD's multi-cpu is not mature yet, but it's growing rapidly.
That's why I whouldn't invest too much in a high-spec machine only to replace it with a higher-spec machine next year.

I wouldn't spend very much on a quad machine, I'd got for two dual machines, or even four single-cpu machines using loadbalancing.