Re: [PATCH] mm: remove zone->prev_prioriy

[KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>]

> On Tue, 10 Feb 2009 19:57:01 +0900
> MinChan Kim <minchan.kim@gmail.com> wrote:
> 
> > As you know, prev_priority is used as a measure of how much stress page reclaim.
> > But now we doesn't need it due to split-lru's way.
> > 
> > I think it would be better to remain why prev_priority isn't needed any more
> > and how split-lru can replace prev_priority's role in changelog.
> > 
> > In future, it help mm newbies understand change history, I think.
> 
> Yes, I'd be fascinated to see that explanation.
> 
> In http://groups.google.pn/group/linux.kernel/browse_thread/thread/fea9c9a0b43162a1
> it was asserted that we intend to use prev_priority again in the future.
> 
> We discussed this back in November:
> http://lkml.indiana.edu/hypermail/linux/kernel/0811.2/index.html#00001
> 
> And I think that I still think that the VM got worse due to its (new)
> failure to track previous state.  IIRC, the response to that concern
> was quite similar to handwavy waffling.

Yes.
I still think it's valuable code.
I think, In theory, VM sould take parallel reclaim bonus.

However, recently, KAMEZAWA-san reported memcg prev_priority code are
busted due to hierarchical-memory-reclaim and he dislike maintain 
unused function.

http://marc.info/?l=linux-mm&m=123258289017433&w=2


and, at that time I can't show good example workload of parallel reclaim bonus
effective.
Therefore I agreed to drop this and insert it again at re-using time ;-)



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