Re: Linux-2.2.0 bad VM behaviour "dd if=/dev/zero of=/dev/hdc

Petri Mattila (petri@prihateam.fi)
Thu, 28 Jan 1999 09:24:18 +0200


At 11:17 AM 1/27/99 -0800, Linus Torvalds wrote:

>This is one of my peeves - we should really start the IO once we've filled
>up "X nr" of full buffers. But I've always been too lazy to do it.

But could somebody please explain why on earth processes get swapped out
if I turn on DMA transfer, but stay in memory with PIO transfer?

With PIO mode the machine is usable, but slow. With DMA mode,
it takes several seconds, sometimes minutes to get a response
for a keystroke, and this happens regardless of memory size.

Petri

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