On Dec 9, 2005, at 12:08 PM, Dave Hansen wrote:
On Fri, 2005-12-09 at 11:55 -0600, Mark Rustad wrote:
On Dec 9, 2005, at 11:16 AM, Dave Hansen wrote:
What driver needs to map huge pages? Is it in the kernel tree
now? If
not, can you post the source, please?
It is a funky driver for an embedded system. I can't imagine it ever
being in the kernel tree, because not many people want to share 768M
of contiguous physical memory.
I can post the source, but it really is a bunch of random stuff for
am embedded application. We do make it available as part of our GPL
source release to customers.
You'd be surprised. If we know what you're actually trying to do, we
might be able to suggest another option. As Adam said, having
userspace
mmap a hugetlb area, then hand it to the driver would certainly keep
your kernel modifications to a minimum.
Actually, the driver never touches any of the memory at all either
directly or indirectly - it simply maps the memory for the processes
that use it. Those processes actually contain PCI device drivers
which do DMA on much of the memory. The same memory also holds data
structures shared by those processes. If hugetlbfs could be
guaranteed to provide contiguous memory for a file, that could be
used in this application. We used to use remap_pfn_range in our
driver, but recent changes there made that not work for this
application, so I figured I may as well switch to huge pages for
these monster areas. At least, gdb was unable to access these large
shared areas, which is a deal-breaker for our developers.
In case you are wondering, these processes were ported onto Linux
from a different, non-x86-based, system that had three cpus which
could directly address each other's memory. They have now been
running happily on top of x86 Linux now for well over a year.
--
Mark Rustad, [email protected]
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