Date: Mon, 21 May 2007 04:37:47 -0700
From: William Lee Irwin III <wli@holomorphy.com>
To: David Miller <davem@davemloft.net>
Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org
Subject: Re: that page count overflow thing
Message-ID: <20070521113747.GK19966@holomorphy.com>
References: <20070519.152649.102577495.davem@davemloft.net>
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On Sat, May 19, 2007 at 03:26:49PM -0700, David Miller wrote:
> I think we may be able to fix that one without making the
> counter larger, it's silly overhead for such an extreme
> case IMHO.
> Perhaps it might be possible to just make the counter stick at it's
> maximum, and when it's there we have an rbtree of external "large"
> counters, keyed by page struct address.
> So basically externalize counters that go over the maximally
> representable value.  In this way only the idiotic cases pay
> the price.

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.


-- wli
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