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

[Andrea Righi]

On 2008-11-05 05:31, KAMEZAWA Hiroyuki wrote:
> On Tue, 4 Nov 2008 19:05:05 -0800
> Andrew Morton <akpm at linux-foundation.org> wrote:
>> Generally, I worry that this is a specific fix to a specific problem
>> encountered on specific machines with specific setups and specific
>> workloads, and that it's just all too low-level and myopic.
>>
>> And now we're back in the usual position where there's existing code and
>> everyone says it's terribly wonderful and everyone is reluctant to step
>> back and look at the big picture.  Am I wrong?
>>
>>
>> Plus: we need per-memcg dirty-memory throttling, and this is more
>> important than per-cpuset, I suspect.  How will the (already rather
>> buggy) code look once we've stuffed both of them in there?
>>
>>
> 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).

-Andrea
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