[Devel] Re: [patch 0/7] cpuset writeback throttling

[Andrew Morton]

On Tue, 4 Nov 2008 16:17:52 -0600 (CST)
Christoph Lameter <cl at linux-foundation.org> wrote:

> On Tue, 4 Nov 2008, Andrew Morton wrote:
> 
> > What are the alternatives here?  What do we need to do to make
> > throttling a per-memcg thing?
> 
> Add statistics to the memcg lru and then you need some kind of sets of 
> memcgs that are represented by bitmaps or so attached to an inode.
> 
> > The patchset is badly misnamed, btw.  It doesn't throttle writeback -
> > in fact several people are working on IO bandwidth controllers and
> > calling this thing "writeback throttling" risks confusion.
> 
> It is limiting dirty pages and throttling the dirty rate of applications 
> in a  NUMA system (same procedure as we do in non NUMA). The excessive 
> dirtying without this patchset can cause OOMs to occur on NUMA systems.

yup.

To fix this with a memcg-based throttling, the operator would need to
be able to create memcg's which have pages only from particular nodes. 
(That's a bit indirect relative to what they want to do, but is
presumably workable).

But do we even have that capability now?

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