Re: [patch 0/7] cpuset writeback throttling

[David Rientjes <rientjes@google.com>]

On Mon, 10 Nov 2008, Andrea Righi wrote:

> > IIUC, Andrea Righ posted 2 patches around dirty_ratio. (added him to CC:)
> > in early October.
> > 
> >   (1) patch for adding dirty_ratio_pcm. (1/100000)
> >   (2) per-memcg dirty ratio. (maybe this..http://lkml.org/lkml/2008/9/12/121)
> >  
> > (1) should be just posted again.
> > 
> > Because we have changed page_cgroup implementation, (2) should be reworked.
> > "rework" itself will not be very difficult.
> > (.... we tend to be stick to "what interface is the best" discussion ;) 
> > 
> > But memcg itself is not so weak against dirty_pages because we don't call
> > try_to_free_pages() becasue of memory shortage but because of memory limitation.
> > 
> > BTW, in my current stack, followings are queued.
> >    a. handle SwapCache in proper way in memcg.
> >    b. handle swap_cgroup (if configured)
> >    c. make LRU handling easier
> > 
> > For making per-memcg dirty_ratio sane, (a) should go ahead. I do (a) now.
> > If Andrea seems to be too busy, I'll schedule dirty_ratio-for-memcg as my work.
> > 
> 
> Hi Kame,
> 
> sorry for my late. If it's not too late tonight I'll rebase and test (1)
> to 2.6.28-rc2-mm1 and start to rework on (2), also considering the
> David's suggestion (split NR_UNSTABLE_NFS from NR_FILE_DIRTY).
> 

The dirty throttling change only depends on patch 1/2 from (2) above, 
which adds the necessary statistics to the memcg for calculating dirty 
ratios.  Patch 2/2 from that series will need to be moved out to a 
separate cgroup as the general consensus from this discussion has 
indicated is necessary.

If it's possible to get a rebased patch 1/2 to add the statistics to the 
memory controller, I'll take it and move the all dirty throttling to a 
separate cgroup so it supports both cpusets and memcg.  Thanks!