Re: [PATCH] Caches that shrink automatically

From: Hans Reiser (reiser@namesys.com)
Date: Sun Aug 04 2002 - 14:17:03 EST


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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