From: Arnd Bergmann <arnd@arndb.de>
To: Catalin Marinas <catalin.marinas@arm.com>
Cc: "linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>,
        Olof Johansson <olof@lixom.net>, "agraf@suse.de" <agraf@suse.de>,
        Will Deacon <Will.Deacon@arm.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] arm64: Enable CONFIG_COMPAT also for 64k page size
Date: Fri, 05 Dec 2014 13:24:49 +0100
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On Friday 05 December 2014 11:05:07 Catalin Marinas wrote:
> 
> > Should we add support for 64k-pages in the arm32 kernel as well now?
> 
> 32-bit LPAE doesn't support 64K pages but IIRC the classic MMU does
> (though I have to check whether it was optional). But it's not feasible
> to enable this in a 32-bit environment because of the memory wasted with
> large pages (on average 32KB per mapped file, possibly even more if you
> have lots of small files).

That sounds like a tradeoff that some users might be willing to make.

I remember that with ps3-linux, a lot of people wanted to enable 64k-pages
because the Cell processor has such a small number of TLB entries (256 or
1024), but Linux only has around 200MB of memory available. I believe
there are arm32 machines with more RAM and fewer TLBs.

	Arnd
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