On Tue, 05 Aug 2008 09:20:18 -0700Dave Hansen <dave@xxxxxxxxxxxxxxxxxx> wrote: > On Tue, 2008-08-05 at 11:28 +0200, Andrea Righi wrote:> > > Buffered write I/O is also related with cache system.> > > We must consider this problem as I/O control.> > > > Agree. At least, maybe we should consider if an IO controller could be> > a valid solution also for these problems.> > Isn't this one of the core points that we keep going back and forth> over? It seems like people are arguing in circles over this:> > Do we:> 1. control potential memory usage by throttling I/O> or> 2. Throttle I/O when memory is full> > I might lean toward (1) if we didn't already have a memory controller.> But, we have one, and it works. Also, we *already* do (2) in the> kernel, so it would seem to graft well onto existing mechanisms that we> have.> > I/O controllers should not worry about memory. I agree here ;) >They're going to have a hard enough time getting the I/O part right. :)> memcg have more problems now ;( Only a difficult thing to limit dirty-ratio in memcg is how-to-count dirtypages. If I/O controller's hook helps, it's good. My small concern is "What happens if we throttole I/O bandwidth too smallunder some memcg." In such cgroup, we may see more OOMs because I/O willnot finish in time.A system admin have to find some way to avoid this. But please do I/O control first. Dirty-page control is related but differentlayer's problem, I think. Thanks,-Kame > Or, am I over-simplifying this?> _______________________________________________Virtualization mailing listVirtualization@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx://lists.linux-foundation.org/mailman/listinfo/virtualization
