[Ocfs2-devel] OCFS2 features RFC

[Andi Kleen <ak@suse.de>]

On Wednesday 26 April 2006 20:06, Mark Fasheh wrote:
> On Wed, Apr 26, 2006 at 06:11:04AM +0200, Andi Kleen wrote:
> > Won't you get into deadlocks then when the system is low on memory?
> > (freeing memory might require write outs on OCFS2 and the user space
> > cluster might be stuck already)
> > 
> > Or rather if you rely on user space you would need to make sure
> > that the basic block write out path works without such possible
> > deadlocks.
> The DLM certainly wouldn't be in userspace - there's also a convincing
> performance argument for it being in kernel.
> 
> Primarily then I think we're worred about that in the context of something
> like heartbeat. In that case, we probably want something that can do it's
> work within some preallocated, mlock'd area. 

That's not enough - it wouldn't be able to do anything that requires
memory allocation in the critical path. This includes most system calls.

> I'm not sure (yet) how the 
> various stacks handle this problem

I suspect they don't.


-Andi