On Mon, May 05, 2003 at 11:33:36AM +0200, Terje Eggestad wrote:
> 1. performance is everything.
> 2. We're making a MPI library, and as such we don't have any control
> with the application.
> 3a. The various hardware for cluster interconnect all work with DMA.
> 3b. the performance loss from copying from a receive area to the
> userspace buffer is unacceptable.
> 3c. It's therefore necessary for HW to access user pages.
> 4. In order to to 3, the user pages must be pinned down.
see how AIO does this, and O_DIRECT, and rawio.
They all have the same requirement and manage to cope.
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