Re: JRebel initially very slow

Hi Q,

On 28.08.2010, at 23:59, Q wrote:
> On 28/08/2010, at 11:06 PM, Marc Guenther wrote:
>> App startup changed from 9sec to 63sec. I think I _could_ live with that, but every click is now also very slow, at least for new pages. What usually takes 2secs (for a slow page) now easily takes 20s.
> 
> While I do notice a slow down, I don't notice anything of this magnitude.

That's good to hear.

> Do you have a massive classpath that causes a huge number of classes to be loaded on "slow pages"?

Not at all. I just checked this again. Every click which leads to a new page takes about 10s or more, and in some of those the jrebel log says it intrumented only one class (the page component itself). It's never more than a couple of classes.

These pages are all <1sec without jrebel. 

>> This only happens on new pages, though, clicks to pages that have been used already are as fast as ever (so once I am where I need to be in my app, its fast, and it works quite nicely).
>> 
>> So I suspect it is something to do with the classloader, and jrebel instrumenting all new classes, or whatever it does. I checked with -Drebel.log=true that it is only instrumenting our own classes, and not the whole of Webobjects. The output of -Drebel.log.perf=true doesn't really tell me anything.
> 
> It may be best to contact zeroturnaround directly about this so that they can look at issue. I have dealt with them directly on several occasions and they have been very helpful. JR does make classloading slower, and adds a small overhead to runtime execution, but unless your are loading a lot of classes it shouldn't be unusably slow.

During app startup, jrebel instruments 637 classes (about half of these are inner classes for the erxkeys in our eogenerated _ classes). First login instruments 33 more classes. From then on it's only 1-5 classes per click.

>> I'm using the most recent jrebel 3.1.2a. I'm on MacOSX 10.6, Java 1.5, Eclipse 3.6 and WOLips 3.6.6116, using WO 5.4.3 (no Wonder)
> 
> How exactly are you using 1.5 on OSX 10.6?  It only ships with and supports 1.6.

Ah, does it :)

I remember that at some point while still on Leopard, Apple decided to silently remove my Java 1.5 installation. So I had to reinstall it manually from the JavaForMacOSX10.5Update6.dmg. I did the same when I installed SnowLeopard and so far it worked without any problems.

(That was also the point that I decided to stop installing any Software Updates from Apple.)

Well, anyway, I just tried it with Java 1.6, and it shows the same behaviour.

>> Is this a problem with my setup, or is it so slow for everybody?
> 
> Is this issue limited to the one application?  In general it shouldn't be that slow unless your application is huge.

I have only that WO application ;) Well, actually it's a bundle of 6, but it happens for all of them.

I will try to setup a test example application and check this.

> One thing I forgot to ask. Does this "slow page" happen to be the first time you fetch from your model(s)?  The initial model load and connection setup to the db can add a noticeable delay because it triggers a large number of classes to be loaded.

No, model loading and everything already happened at startup.

I'm contacting jrebel support now, and let you know what they say.

Thanks,
Marc