Comments on: Say it Ain’t So Memcache

By: vdibart

vdibart — Mon, 24 Aug 2009 02:19:41 +0000

@Dustin: A little background would help. I have a bunch of PHP objects that represent stats and detail information for each MLB player – so position name, team name, batting average, stolen bases, etc. For simplicity’s sake, assume some other process created these objects and stored them for use in various places across the application. So the comparison was:

1) querying all the player detail information for a random subset of players (including an inner join across a handful of tables), creating and populating objects, then returning them to the view layer

2) querying for just player IDs for a random subset of players (including a very straightforward query with possibly 1 join), then pulling the objects for those player IDs out of memcache.

As I mention, the memory issue was almost as important as the other ones because I would have thought memcache would have reduced memory consumption, but of course that seems naive now. Those objects have to decompressed, marshalled, whatever, and all that happens in memory.

By: vdibart

vdibart — Mon, 24 Aug 2009 02:09:56 +0000

Memcache was running on the web/php slice. Sorry, should have included that above.

By: Steve Yen

Steve Yen — Sat, 22 Aug 2009 20:53:13 +0000

Interesting results. I’m wondering which slice was your memcached server was running? On your web/php slice or database slice?

By: Dustin Sallings

Dustin Sallings — Sat, 22 Aug 2009 05:52:24 +0000

Well, without seeing your code, I can only guess that you’re doing a PK lookup on a table from a DB pool and comparing it to connecting to a memcached server and issuing a single request and disconnecting.

There are places where memcached will help you a lot, and places where it doesn’t provide much value. You should start by measuring the places where you’re spending a lot of time in the DB, or constructing an object that requires multiple database queries.

(probably won’t see any responses as I typically don’t comment on random blogs since I can’t track easily track responses)