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Date: Fri, 07 Dec 2001 19:46:51 -0800
From: "H. Peter Anvin" <hpa@zytor.com>
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To: war <war@starband.net>
CC: Jens Axboe <axboe@suse.de>, Marvin Justice <mjustice@austin.rr.com>,
        linux-kernel@vger.kernel.org
Subject: Re: highmem question
In-Reply-To: <Pine.LNX.4.30.0112071404280.29154-100000@mustard.heime.net> <01120719534703.00764@bozo> <20011208015446.GC32569@suse.de> <01120720102404.00764@bozo> <20011208021040.GE32569@suse.de> <3C118C6B.33EA558F@starband.net>
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war wrote:

> I have 1GB of ram + HIGHMEM support on.
> 
> How much of a performance impact are we talking about?
> 
> 896MB of ram would be ok if HIGHMEM impacted the machine severely.
> 
> Has anyone done any benchmarks with HIGHMEM vs NO HIGHMEM?
> 


1 GB is really the worst case.  You don't gain too much memory this way, 
and suffer the necessary slowdown.

Personally I would support dropping the kernel boundary to 0xb8000000 
and use 0xb8000000-0xbfffffff for iomem; that way 1 GB wouldn't need 
HIGHMEM.

	-hpa


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