linux-kernel - Re: that page count overflow thing

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Message-ID: <20070521121634.GM19966@holomorphy.com>
Date:	Mon, 21 May 2007 05:16:34 -0700
From:	William Lee Irwin III <wli@...omorphy.com>
To:	David Miller <davem@...emloft.net>
Cc:	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: that page count overflow thing

> From: William Lee Irwin III <wli@...omorphy.com>
> Date: Mon, 21 May 2007 04:37:47 -0700
>> This could be awkward with allocation requirements. How about an
>> open-addressed hash table? It can be made so large as to never
>> need to expand in advance with a very small constant factor space
>> overhead.

On Mon, May 21, 2007 at 04:50:31AM -0700, David Miller wrote:
> I was just thinking of a normal hash table with entries that
> looked simply like:
> struct page_big_count_hash {
>        struct page_big_count_hash *next; /* or list_head or hlist_head etc. */
>        struct page *key;
>        atomic64_t count;
> };

I guess that could work with a static pool of hashtable elements like
mm/highmem.c uses, but the pointer links seem like such a waste of space.
It'll work, so no big deal. Maybe converting mm/highmem.c to hashing by
open addressing would be a simplification. Not worth disturbing working
code, though.


-- wli
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