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Re: Anyone noticed that there are a lot of cache flushes after kunmap/ku

To: jfraser@broadcom.com
Subject: Re: Anyone noticed that there are a lot of cache flushes after kunmap/kunmap_atomic is called?
From: David VomLehn <dvomlehn@cisco.com>
Date: Mon, 11 Aug 2008 16:19:03 -0700
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Cc: Ralf Baechle <ralf@linux-mips.org>, linux-mips@linux-mips.org, michael.sundius@sciatl.com
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Jon Fraser wrote:
David,

  I'm battling this now.  Our mips 24k has a virtually indexed cache.
We're definitely seeing issues where the cache hasn't been flushed
for highmem pages.  I thought I had this fixed, but I'm still seeing
some problems.

As I understand it, you have the most difficult combination of things:
o You are using high memory
o You have a virtually indexed cache
o You have data cache aliases

Fortunately, we have only the first two of those in our system. We should probably put together a coherent set of patches for people who want high memory. So far as I can tell, the 32-bit MIPS architecture has a long way to go before it runs out of steam in the embedded world. I expect more people will need MIPS highmem support in the next few years.

David


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