[imp] Slow mailbox list from time to time

[Andrew Morgan]

On Fri, 5 Jun 2009, lst_hoe02 at kwsoft.de wrote:

> Zitat von Tornoci Laszlo <torlasz at xenia.sote.hu>:
>
>> lst_hoe02 at kwsoft.de wrote:
>>> Zitat von Tornoci Laszlo <torlasz at xenia.sote.hu>:
>>> 
>>>> Hi,
>>>> 
>>>> I have a Horde/IMP system that behaves strangely since I upgraded from 
>>>> 3.1.5/4.1.5 to 3.3.4/4.3.4. I have about 400 users with 50-70 concurrent 
>>>> sessions usually. The IMAP mailstore (Cyrus) and the MTA are on separate 
>>>> boxes. The system is dual Xeon (quad core) 2GHz, 2GB RAM.
>>>> 
>>>> We had excellent response times before the upgrade. The problem is, we 
>>>> still have excellent response times (practically instantaneous mailbox 
>>>> lists with > 3000 mails in one folder) most of the time, BUT sometimes 
>>>> for long periods of time, I get miserable response times (30-80 sec 
>>>> waiting) for the same large mailbox to be listed. "top" show the http 
>>>> process to shoot up to 100% cpu while waiting, but nothing else 
>>>> remarkable. Restarting http or mysqld doesn't help. Logging in is not 
>>>> slow. The larger a mailbox, the worse the problem is.
>>>> After some time, response times get back to normal.
>>> 
>>> It *may* be Horde Alarms. As far as i remember there was a problem with 
>>> the way Horde Alarms uses the Database in some configurations but i can't 
>>> remember for sure. This could explain why you see it only occasionally. 
>>> Another point to check is if you are using a PHP accelerator which do 
>>> maintenance at the slow times.
>> 
>> Thanks for the tip, I've disabled the alarms, I'll see if it makes any 
>> difference. I don't use any PHP accelerators (by the way: are there any 
>> reliable ones that are free?)
>
> We use APC from pecl.php.net and have not yet found any problems, but our 
> sites are not loaded that much. If you have enough RAM every PHP accelerator 
> will help keep your CPU cool.

APC works great here.  It makes a huge performance improvement.  I set the 
cache size to 96MB, and it is using about 60MB of it right now.

 	Andy