On my continuing series of me poking around at ways to improve performance…<\/p>\n
I accidentally stumbled across something on memcached<\/a>. The classic example is LiveJournal (which, incidentally, created memcached for their needs). It’s extraordinarily<\/em> database-intensive, and spread across dozens of servers. For what they were doing, generating HTML pages didn’t make sense that often. So it does something creative: it creates a cache (in the form of a hash table) that works across a network. You might have 2GB of RAM to spare on your database server (actually, you shouldn’t?) and 1GB RAM you could use on each of 6 nodes. Viola, 8 GB of cache. You modify your code to ask the cache for results, and, if you don’t get a result, then you go get it from the database (or whatever) as usual.<\/p>\n But what about situations like mine? I have one server. And I use MySQL query caching. But it turns out it’s useful. (One argument for using it is that you can just run multiple clients on a single server to render moot any problems with using more than 4GB on a 32-bit system… But I’m not lucky enough to have problems with not being able to address my memory.)<\/p>\n MySQL’s query cache has one really irritating “gotcha”–it doesn’t catch TEXT and BLOB records, since they’re of variable length. Remembering that this is a blog, consisting of lots and lots of text, you’ll quickly see my problem: nearly every request is a cache miss. (This is actually an oversimplification: there are lots<\/em> of less obvious queries benefiting, but I digress.) (WordPress complicates things by insisting on using the exact timestamp in each query, which also renders a query cache useless.) I just use SuperCache on most pages, to generate HTML caches, which brings a tremendous speedup.<\/p>\n But on the main page, I’m just hitting the database directly on each load. It holds up fine given the low traffic we have, but “no one uses it” isn’t a reason to have terrible performance. I’ve wanted to do some major revising anyway, so I think a rewrite in my spare time is going to experiment with using memcached to improve performance.<\/p>","protected":false},"excerpt":{"rendered":" On my continuing series of me poking around at ways to improve performance… I accidentally stumbled across something on memcached. The classic example is LiveJournal (which, incidentally, created memcached for their needs). It’s extraordinarily database-intensive, and spread across dozens of … Continue reading