On Wednesday 17 January 2007 15:36, Paul Jackson wrote: > > With a per node dirty limit ... > > What would this mean? > > Lets say we have a simple machine with 4 nodes, cpusets disabled.
There can be always NUMA policy without cpusets for once. > Lets say all tasks are allowed to use all nodes, no set_mempolicy > either. Ok. > If a task happens to fill up 80% of one node with dirty pages, but > we have no dirty pages yet on other nodes, and we have a dirty ratio > of 40%, then do we throttle that task's writes? Yes we should actually. Every node should be able to supply memory (unless extreme circumstances like mlock) and that much dirty memory on a node will make that hard. > I am surprised you are asking for this, Andi. I would have thought > that on no-cpuset systems, the system wide throttling served your > needs fine. No actually people are fairly unhappy when one node is filled with file data and then they don't get local memory from it anymore. I get regular complaints about that for Opteron. Dirty limit wouldn't be a full solution, but a good step. > If not, then I can only guess that is because NUMA > mempolicy constraints on allowed nodes are causing the same dirty page > problems as cpuset constrained systems -- is that your concern? That is another concern. I haven't checked recently, but it used to be fairly simple to put a system to its knees by oversubscribing a single node with a strict memory policy. Fixing that would be good. -Andi - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
