KAMEZAWA Hiroyuki wrote: > On Tue, 05 Aug 2008 09:20:18 -0700 > Dave 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 dirty > pages. If I/O controller's hook helps, it's good. > > My small concern is "What happens if we throttole I/O bandwidth too small > under some memcg." In such cgroup, we may see more OOMs because I/O will > not 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 different > layer's problem, I think. Yes, please solve the I/O control problem first. -- Warm Regards, Balbir Singh Linux Technology Center IBM, ISTL -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
