Messages in this thread | | | From | Andrea Righi <> | Subject | Re: Too many I/O controller patches | Date | Tue, 5 Aug 2008 11:31:47 +0200 (MEST) |
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Hirokazu Takahashi wrote: > Hi, Andrea, > > I'm working with Ryo on dm-ioband and other stuff. > >>> On Mon, 2008-08-04 at 20:22 +0200, Andrea Righi wrote: >>>> But I'm not yet convinced that limiting the IO writes at the device >>>> mapper layer is the best solution. IMHO it would be better to throttle >>>> applications' writes when they're dirtying pages in the page cache (the >>>> io-throttle way), because when the IO requests arrive to the device >>>> mapper it's too late (we would only have a lot of dirty pages that are >>>> waiting to be flushed to the limited block devices, and maybe this could >>>> lead to OOM conditions). IOW dm-ioband is doing this at the wrong level >>>> (at least for my requirements). Ryo, correct me if I'm wrong or if I've >>>> not understood the dm-ioband approach. >>> The avoid-lots-of-page-dirtying problem sounds like a hard one. But, if >>> you look at this in combination with the memory controller, they would >>> make a great team. >>> >>> The memory controller keeps you from dirtying more than your limit of >>> pages (and pinning too much memory) even if the dm layer is doing the >>> throttling and itself can't throttle the memory usage. >> mmh... but in this way we would just move the OOM inside the cgroup, >> that is a nice improvement, but the main problem is not resolved... > > The concept of dm-ioband includes it should be used with cgroup memory > controller as well as the bio cgroup. The memory controller is supposed > to control memory allocation and dirty-page ratio inside each cgroup. > > Some guys of cgroup memory controller team just started to implement > the latter mechanism. They try to make each cgroup have a threshold > to limit the number of dirty pages in the group.
Interesting, they also post a patch or RFC?
-Andrea
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