Messages in this thread | | | Date | Fri, 07 Dec 2001 17:58:16 -0800 | From | "H. Peter Anvin" <> | Subject | Re: highmem question |
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Jens Axboe wrote:
> 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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