WP-Super-Cache: Memory and CPU Hog?
Posted September 26th, 2008 @ 12:51pm by Erik J. Barzeski
WP-Super-Cache is considered by many to be one of the "must-have" plugins for WordPress.
Yet if my recent experience says anything, it's that WP-Super-Cache causes nothing but trouble: it bizarrely interferes with the rendering of pages and it sucks up obscene amounts of CPU time and RAM.
On the first issue, several times throughout my use of WP-Super-Cache (and WP-Cache before it), pages would fail to render properly - most often because the output would simply stop at some point, leaving out the trailing 10 to 90% of the page - with the plugin installed and active. Disabling the plugin fixed the rendering issue in every instance, while doing things like clearing the cache (both within the plugin and on your browser) would not.
And lately, I've been a bit annoyed that my server was reaching some limits for both CPU load as well as memory. At one point, WP-Super-Cache was preventing 100% of the page from loading, so I disabled it, and instantly and for several days now, load and memory usage have dropped below the levels at which they've held steady for the past several months.
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Posted 27 Sep 2008 at 1:50pm #
So which solution do you recommend if you have to scale a WordPress installation? I think WordPress isn't really focused on scaling and performance issues, but there should be at least a possibility to have something in between.
Posted 27 Sep 2008 at 2:06pm #
At this point, I recommend nothing. This site may not see many hits per day, but The Sand Trap sees tens of thousands and seems to hold up just fine.
Posted 28 Sep 2008 at 9:40am #
I think the most important factor is the scalability of your web hosting provider. If you go with the cheapest one, you'll have problems - at least if you'll have visitor peaks.
Posted 28 Sep 2008 at 10:20am #
[quote comment="49875"]I think the most important factor is the scalability of your web hosting provider. If you go with the cheapest one, you'll have problems - at least if you'll have visitor peaks.[/quote]
I don't have a cheap web host, so I'm not sure how that applies or why you felt it necessary to say it here. WP-Super-Cache might help someone with a cheap host, but in my case, it uses more RAM and resources than not having it installed. 5-10x fewer resources, in fact.
Posted 28 Sep 2008 at 3:48pm #
Give the development version a go, it's linked off the "Other versions" download page on the WordPress.org page for the plugin.
I fixed a bug where the content was being compressed twice which should help with our problems.
Unfortunately the plugin does need to load the entire generated page to compress it which does take up memory, and cache maintenance (garbage collection, etc) does take up resources and is unavoidable.
Posted 18 Oct 2008 at 8:33pm #
I haven't experienced any problems at all with the plugin. That said, I also haven't seen any speed increase in how fast my pages load with it on so I disabled it. I've heard that my host can handle it okay if I get Digged/Slashdotted.
WordPress has it's own internal caching. In order to make use of it, and to reduce the number of queries on your site, you may need to add the following to your wp-config.php :
define('ENABLE_CACHE', true);