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

[Erick Tryzelaar]

On Thu, Apr 9, 2009 at 3:03 PM, Erick Tryzelaar
<idadesub at users.sourceforge.net> wrote:
> Good afternoon,
>
> We're running into some pretty severe performance issues with gluster
> when we're using io-cache on the server side. We're just doing some
> basic performance measuring between one server and one client. Here's

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?