question about xcache

I spent the last few days working with my web host tech support to get xcache installed on my VPS. I've got four different vbulletin sites running on this server.

Q1) Is just having xcache installed (cache size = 32MB) going to improve performance for all 4 sites, or does the improvement only come with moving the data store to xcache?

Q2) I set the data store for the least busy forum to xcache to test it. It worked. I then set the data store for another to xcache and saw that the site was all confused (drawing from the cached data of the first site). I reset both forums to not use the xcache data store. I would like to set a different forum to use the xcache data store, but I need to reset/clear the cache first. How can I do that?

Q3) Would it be better to not set any of the forums to use xcache for the data store (leaving more cache room for PHP caching in general)?

If you are going to use multiple sites you may want to increase the setting to 128mb

Also you need to define a datastore class for each of your forum within config.php

PHP Code:

    // ******** DATASTORE PREFIX ******
    // If you are using a PHP Caching system (APC, XCache, eAccelerator) with more
    // than one set of forums installed on your host, you *may* need to use a prefix
    // so that they do not try to use the same variable within the cache.
    // This works in a similar manner to the database table prefix.
// $config['Datastore']['prefix'] = ''; 


I don't have enough memory on my VPS account to increase the cache that much. I currently only see ~60MB free memory available.

I tried setting the datastore for two forums via config.php as you suggested and the second one started showing the forum list from the first one - they got all comingled/confused. The second forum was reading the cache data from the first forum. Not good at all...

Any chance you can answer my questions?

Oh snap! I just realized you quoted code referencing a prefix. I don't see that code block in my 3.7.0 config.php file. Perhaps it's something they added to 3.7.2...

As far as i remember it was added long time ago. Make sure your config.php is updated.

What about the xcache option in vbSEO? Does it use the vB prefix, or is there another method in place to allow for more than one vBSEO'd forum?

How much cache space do I really need per forum (for vB and vBSEO)?

There is an option in config_vbseo.php to specify XCache variable name for vBSEO:

PHP Code:

    define('VBSEO_CACHE_VAR',              'vbseo_storage'); 


How much cache space do I really need per forum (for vB and vBSEO)?

You can enable caching for a while and then check in xcache admin how much memory does it actually use.

Great. Thanks!

Another n00b question...

I'm seeing OOMs in the xcache admin. What do I need to do after editing php.ini to make any changes/adjustments take hold? Do I need to restart apache?

Nevermind, restarting apache did the trick.

Another question...

My VPS does not have a lot of memory available. I've currently got xcache.size=88M and xcache.var_size=0M. xcache admin indicates the cache has about 12M free after running for 30 minutes or so. It seems to be holding steady around that number right now. WHM indicates that I have anywhere from 24-40M free memory for the server.

What I'd like to know is, if I add 16M or so to the xcache.var_size and then set a vB datastore to use xcache (and/or set vBSEO to use xcache), is that necessarily going to reduce the load/usage of the xcache opcode memory? Or should I just consider that 16MB as memory that is going to be used on top of the opcode cache?

oom = out of memory. if you have more than a couple, you should up the available size.

Thanks Brian, I've been tinkering with it. I had to upgrade my hosting with more memory to get everything working properly, but it's really flying now.