Date: Wed, 7 Dec 2005 18:36:44 +0800
From: Wu Fengguang <wfg@mail.ustc.edu.cn>
To: Andrew Morton <akpm@osdl.org>
Cc: nikita@clusterfs.com, Linux-Kernel@vger.kernel.org
Subject: Re: [PATCH 01/16] mm: delayed page activation
Message-ID: <20051207103643.GA4335@mail.ustc.edu.cn>
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	Andrew Morton <akpm@osdl.org>, nikita@clusterfs.com,
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On Wed, Dec 07, 2005 at 01:46:59AM -0800, Andrew Morton wrote:
> Wu Fengguang <wfg@mail.ustc.edu.cn> wrote:
> >
> > Andrew, and anyone in the lkml, do you feel ok to test it in -mm tree?
> 
> Nope, sorry.  I am wildly uninterested in large changes to page reclaim. 
> Or to readahead, come to that.
> 
> That code has had years of testing, tweaking, tuning and poking.  Large
> changes such as these will take as long as a year to get settled into the
> same degree of maturity.  Both of these parts of the kernel are similar in
> that they are hit with an extraordinarly broad range of usage patterns and
> they both implement various predict-the-future heuristics.  They are subtle
> and there is a lot of historical knowledge embedded in there.
> 
> What I would encourage you to do is to stop developing and testing new
> code.  Instead, devote more time to testing, understanding and debugging
> the current code.  If you find and fix a problem and can help us gain a
> really really really good understanding of the problem and the fix then
> great, we can run with that minimal-sized, minimal-impact, well-understood,
> well-tested fix.
> 
> See where I'm coming from?  Experience teaches us to be super-cautious
> here.  In these code areas especially we cannot afford to go making
> larger-than-needed changes because those changes will probably break things
> in ways which will take a long time to discover, and longer to re-fix.

Ok, thanks for the advise.
My main concern is in read-ahead. The new development stopped roughly from V8. 
Various parts have been improving based on user feedbacks since V6. The future
work would be more testings/tunings and user interactions. Till now I have
received many user reports on both server/desktop, things are going on well :)

Regards,
Wu
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