Messages in this thread | | | Date | Wed, 11 Feb 2009 03:12:01 -0800 | From | Andrew Morton <> | Subject | Re: [PATCH] mm: remove zone->prev_prioriy |
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On Wed, 11 Feb 2009 20:06:46 +0900 (JST) KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> wrote:
> > 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.
prev_priority had nothing to do with concurrent reclaim?
It was there so that when a task enters direct reclaim against a zone, it will immediately adopt the state which the task which most recently ran direct reclaim had.
Without this feature, each time a task enters direct reclaim it will need to "relearn" that state - ramping up, making probably-incorrect decisions as it does so.
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