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Date: Sun, 28 Jul 2002 18:04:03 -0700
From: William Lee Irwin III <wli@holomorphy.com>
To: Andrea Arcangeli <andrea@suse.de>
Cc: Andrew Morton <akpm@zip.com.au>,
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Subject: Re: [BK PATCH 2.5] Introduce 64-bit versions of PAGE_{CACHE_,}{MASK,ALIGN}
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On Sun, Jul 28, 2002 at 05:43:25PM -0700, William Lee Irwin III wrote:
>> This is so aggressive I'm obligated to pursue it. The pte_chain will
>> die shortly if I get my way as it is.

On Mon, Jul 29, 2002 at 02:56:12AM +0200, Andrea Arcangeli wrote:
> if you look at DaveM first full rmap implementation it never had a
> pte-chain. He used the same rmap logic we always hand in linux since the
> first 2.1 kernel I looked at, to handle correctly truncate against
> MAP_SHARED. Unfortunately that's not very efficient and requires some
> metadata allocation for anonymous pages (that's the address space
> pointer, anon pages regularly doesn't have a dedicated address space),
> and overhead that we never had w/o full rmap (and for inode backed
> mappings we just have this info in the inode, just the shared_lock
> locking isn't trivial). Hope you can came up with a better algorithm
> (nevertheless also the current rmap implementation adds significant
> measurable overhead in the fast paths), Rik told me a few days ago he
> also wanted to drop the pte_chain, but I assume you're just in sync with him.

I've seen davem's implementation. The anonymous page metadata
allocations, while they are overhead, are likely to be significantly
smaller than per-pte overhead. The rest is a matter of details. You're
welcome to participate with the design and/or implementation.


Cheers,
Bill
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