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Re: sparsemem support for mips with highmem

To: David VomLehn <>
Subject: Re: sparsemem support for mips with highmem
From: Christoph Lameter <>
Date: Tue, 19 Aug 2008 08:06:21 -0500
Cc: Randy Dunlap <>, C Michael Sundius <>, Dave Hansen <>, Thomas Bogendoerfer <>,,,, Andy Whitcroft <>
In-reply-to: <>
Original-recipient: rfc822;
References: <> <1218753308.23641.56.camel@nimitz> <> <> <1218815299.23641.80.camel@nimitz> <> <> <> <1218821875.23641.103.camel@nimitz> <> <> <> <>
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David VomLehn wrote:

> On MIPS processors, the kernel runs in unmapped memory, i.e. the TLB
> isn't even
> used, so I don't think you can use that trick. So, this comment doesn't
> apply to
> all processors.

In that case you have a choice between the overhead of sparsemem lookups in
every pfn_to_page or using TLB entries to create a virtually mapped memmap
which may create TLB pressure.

The virtually mapped memmap results in smaller code and is typically more
effective since the processor caches the TLB entries.

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