Magento

Hi all,

With so much being talked about APC improving the site performance, I decided to give it a try. And was a bit disappointed to note that the UI all of a sudden give a blank page - ex. once the user clicks on Add to Cart, the page turns blank!!!

Was worried and took me some time to realize that it was APC that was causing this issue!!! Read a bit more and found this article which confirmed my hunch. APC is prone to Segmentation fault errors that result in blank pages

OP Code Caches

Wonder why this is being recommended when this kind of a problem exists or is there a workaround to this segmentation faults?

We have not experienced segmentation faults with APC on linux platforms.

There were few under Windows server though, and i think it was covered in one of the board posts or wiki articles.

Our choice of APC over eAccelerator is because eAccelerator had problems handling exceptions in PHP5 during out tests.

Thanks Moshe for replying. I am on apache 2.x. A CentOS5 and I face this issue ...is there any workaround? Which linux was APC tested upon in your case?

srinigenie - 12 May 2008 11:24 AM

Thanks Moshe for replying. I am on apache 2.x. A CentOS5 and I face this issue ...is there any workaround? Which linux was APC tested upon in your case?

Hello,

There are known compatibility issues with APC & Zend Optimizer 3.x - The end result is exactly as you have described.

You will get better performance by using eAccellerator as well.

Hope this helps some.

How about XCache? I read a lot of good things about XCache as well.. ... does Magento require some code that needs to help in caching? Does this mean Magento can be cached with APC only? Wonder why as the op-code cache mechanisms should be able to cache any PHP script for that matter!!

Hello,

srinigenie - 12 May 2008 11:59 AM

How about XCache? I read a lot of good things about XCache as well

I dont have any direct experience with xcache so I really can’t comment on it - might be worth a try.

does Magento require some code that needs to help in caching?

No, this is done at the server level and controlled by configuration.

Does this mean Magento can be cached with APC only?

No, not at all.  The incompatibility has nothing to do with Magento.  Quite simply put, APC Cache is not compatible with Zend Optimizer.  If you wish to use APC you will need to disable zend optimizer.

Wonder why as the op-code cache mechanisms should be able to cache any PHP script for that matter!!

This is how the op caches work - I am not certain I understand.

Our testing showed no advantage to using APC while having the rather large disadvantage of not being able to support Zend Optimizer for other applications/clients.

thanks Crucial !! One reason why I suspected that Magento code is written for APC is the latest release notes Magento 1.0.19870 (May 8, 2008) - has a line saying
“Fixed APC cache backend”

srinigenie - 12 May 2008 06:27 PM

One reason why I suspected that Magento code is written for APC is the latest release notes Magento 1.0.19870 (May 8, 2008) - has a line saying
“Fixed APC cache backend”

Actually these are two different things. First is PHP code (bytecode) caching, and the second is caching data in Magento.

You can use any bytecode caching solution (APC, eAccelerator, xCache, ZendPlatform/ZendOptimizer), if it works ok for you. We tested Magento only under APC and eAccelerator. The last had some issues with exception handling in PHP5 that time, but it might be already fixed.

Magento data caching can be implemented with a few backends at the moment:
- filesystem cache (by default)
- using filesystem cache on in-memory filesystems (tmpfs, etc)
- APC
- memcached

Filesystem cache usually shows lower performance, but it can work in any environment and it doesn’t require you to install any additional software or to have any specific knowledge on server configuration.