>>>> Marcus Rueckert <darix@opensu.se> 8/17/2010 12:03 PM >>>
>On 2010-08-17 11:14:03 -0600, Matthew Ehle wrote:
>>>APC Caching can show a major improvement in MediaWikis... at least 4x.
>>>If APC is not turned on, it probably should be.
>>
>> APC opcode caching was added for all the openSUSE blogs and wikis back
>> in November, and it has been a major improvement. I shudder to think
>> of how the new wiki would run without it.
>>
>> However, this does bring up another point. Right now, we cache
>> variables with memcached. We could switch variable caching to APC,
>> which is arguably faster. This would most likely be a very minor
>> improvement, but it is a possibility.
>
>I highly doubt that apc cache is much faster than memcached.

It mostly depends on how the wiki is used (amount of read vs. write), but the general consensus is that APC is slightly faster for most situations.

>In a proper config you got one memcached per webserver, and configure
>all memcacheds in the wiki.

Each web server has its own memcached daemon, which is used by only that web server. We can always pool them, but it would make very little difference for our setup.

>a) you got shared storage, no matter on which webserver you get the
>request. I would assume that the APC is local to the machine.

Yes, and that is why it is slightly faster. APC is accessed locally, while memcached is accessed through a network socket, even on localhost.

>b) you can scale to much more cache with memcached than with APC.

Yes, but we don't have enough data for that to be relevant quite yet. I run memcached to store up to 1GB of data, but I don't think we even come close to hitting that.

>c) memcached is fast enough for wikipedia and even facebook (although
>they use it with udp in the mean time)

Agreed. I think that it is a perfectly acceptable solution. I just wanted to bring up the APC alternative as a possibility. I might have to look into running memcached with UDP, as that might cut some of the network overhead.