Re: [PATCH 2.5] SGI O2 framebuffer driver

[Ralf Baechle <ralf@linux-mips.org>]

On Thu, Dec 12, 2002 at 12:44:05PM +0000, Alan Cox wrote:

> > The O2 is non-cache coherent.  So with the fairly large write-back second
> > level caches enabled frame buffer write could potencially be delayed
> > indefinately but in any case quite long.  Frame buffers are usually only
> 
> You can flush the frame buffer pages that were touched at the end of an
> operation though

Flushes are very expensive operations, on the order of 16 cycles per
cacheline plus memory delay.  So why using them when just using the right
cache mode does the right thing already.

  Ralf