On 04/11/2013 09:54 PM, Simon Jeons wrote:
Hi Jerome,
On 04/12/2013 02:38 AM, Jerome Glisse wrote:
On Thu, Apr 11, 2013 at 11:42:05AM +0800, Simon Jeons wrote:
Tomorrow world we want gpu to be able to access memory that the
application
allocated through a simple malloc and we want the kernel to be able to
recycly any page at any time because of memory pressure or because kernel
decide to do so.
That's just what we want to do. To achieve so we are getting hw that
can do
pagefault. No change to kernel core mm code (some improvement might be
made).
The memory disappear since you have a reference(gup) against it,
correct? Tomorrow world you want the page fault trigger through iommu
driver that call get_user_pages, it also will take a reference(since gup
is called), isn't it? Anyway, assume tomorrow world doesn't take a
reference, we don't need care page which used by GPU is reclaimed?
The GPU and CPU may each have a different page table format.
The kernel will need to keep both in sync. That is one of the
things this discussion is about.
For performance reasons, it may also make sense to locate some
of the application's data in the GPU's own memory, so it does
not have to cross the PCIE bus every time it needs to load the
data. That requires memory coherency code in the kernel.
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