Re: Too many I/O controller patches
From: Balbir Singh <hidden>
Date: 2008-08-06 03:30:07
KAMEZAWA Hiroyuki wrote:
On Tue, 05 Aug 2008 09:20:18 -0700 Dave Hansen [off-list ref] wrote:quoted
On Tue, 2008-08-05 at 11:28 +0200, Andrea Righi wrote:quoted
quoted
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 ;)quoted
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 _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linux-foundation.org/mailman/listinfo/virtualization