[Gluster-users] severe performance io-cache bug with large cache in rc7 and git?

[Anand Avati]

> I've done some more research and this appears to be linked with the
> page size somehow. At the default 128KB, it does the pattern
> previously described. When we go up to 512KB, the problem goes away
> and the glusterfsd's %cpu still grows, but it grows at a much slower
> rate. At 256KB, the %cpu growth is in between the two. With a 6GB test
> file and 256KB page file, we get the same performance problems as
> before. If I raise the page size to 1MB and copy the 6GB file, the
> %cpu grows very slowly and the copy performance doesn't drop,
> following the pattern. Maybe we're running into a lot of hash
> collisions in the cache data structure?

Your analysis is right. In fact, the current version uses a sorted
list to store pages. It has been in our to-do list to convert this to
a B-Tree. It is planned for the next release (2.0.1)

Avati