Re: Getting big areas of memory, in 2.3.x?

["William J. Earl" <wje@cthulhu.engr.sgi.com>]

Alan Cox writes:
 > >      That is not the case for loadable (modular) drivers.  Loading st
 > > as a module, for example, after boot time sometimes works and sometimes does
 > > not, especially if you set the maximum buffer size larger (to, say, 128K,
 > > as is needed on some drives for good space efficiency).
 > 
 > Dont mix up crap code with crap hardware. Scsi generic had similar problems
 > and has been fixed. There are very very few non scatter-gather scsi controllers

      I only mentioned st as example of the inability to get a large page
long after system startup.  Large pages are good for a variety of purposes.
For example, large pages for programs with large code or data footprints
can dramatically reduce TLB misses.  If the I/O system learns to do direct
I/O, the overhead of setting up large I/O operations, whether for disk I/O
or for OpenGL operations such as writing a large image to the screen
(via DMA), is much reduced when the I/O is done from large pages.
The CPU overhead of setting up I/O operations is pretty minimal when you
are doing file I/O to and from a single IDE disk, but far from minimal
for higher-bandwidth targets, such as a graphics controller or a 
HDTV camera.

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