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Date: Sun, 04 Aug 2002 23:17:03 +0400
From: Hans Reiser <reiser@namesys.com>
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To: Linus Torvalds <torvalds@transmeta.com>
CC: Rik van Riel <riel@conectiva.com.br>, Andreas Gruenbacher <agruen@suse.de>,
       Alan Cox <alan@redhat.com>, Marcelo Tosatti <marcelo@conectiva.com.br>,
       lkml <linux-kernel@vger.kernel.org>,
       Joshua MacDonald <jmacd@namesys.com>
Subject: Re: [PATCH] Caches that shrink automatically
References: <Pine.LNX.4.44.0208041202390.10314-100000@home.transmeta.com>
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Linus Torvalds wrote:

>On Sun, 4 Aug 2002, Rik van Riel wrote:
>  
>
>>>In particular, it is useless for the sub-caches to try to maintain their
>>>own LRU lists and their own accessed bits. But that doesn't mean that
>>>they can _act_ as if they updated their own accessed bits, while really
>>>just telling the page-based thing that that page is active.
>>>      
>>>
>>I'm not sure I agree with this.  For eg. the dcache you will want
>>to reclaim the less used entries on a page even if there are a few
>>very intensely used entries on that page.
>>    
>>
>
>True in theory, but I doubt you will see it very much in practice. 
>
>Most of the time when you want to free dentries, it is because you have a 
>_ton_ of them. 
>
>The fact that some will look cold even if they aren't should not matter 
>that much statistically.
>
>Yah, it's a guess. We can test it.
>
>		Linus
>
>
>
>  
>
Josh tested it.  He posted on it.  I'll have him find his original post 
and repost tomorrow, but summarized in brief, the current dcache 
shrinking/management approach was quite inefficient.  Each active dcache 
entry kept a whole lot of dead ones around.

-- 
Hans



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