> On Fri, Dec 07 2001, Marvin Justice wrote:
>
>>>There is no way of fixing it.
>>>
>>All I know is that a streaming io app I was playing with showed a drastic
>>performance hit when the kernel was compiled with CONFIG_HIGHMEM. On W2K we
>>saw no slowdown with 2 or even 4GB of RAM so I think solutions must exist.
>>
>
> That's because of highmem page bouncing when doing I/O. There is indeed
> a solution for this -- 2.5 or 2.4 + block-highmem-all patches will
> happily do I/O directly to any page in your system as long as your
> hardware supports it. I'm sure we're beating w2k with that enabled :-)
>
I didn't realize we were doing page bouncing for I/O in the 1-4 GB range.
Yes, this would be an issue.
-hpa
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