Re: page locking in PowerPC cores

--- Eugene Surovegin <ebs@ebshome.net> wrote:

quoted

  We allocate memory for DMA operation on PCI

device using pci_alloc_constistent().

quoted

   
  I want to know how this function is boil down to

the actual instruction which locks the page in the
RAM so that it cannot be paged out and dma can do
its work.

This is trivial - you can start with looking at the
implementation.

[Parav]
I did it, but after reaching __alloc_pages() its
getting difficult to understand.
Here is the sequence:
pci_alloc_consistent()
-> __get_free_pages()
   ->alloc_pages(gfp_mask, order)
      ->alloc_pages_current()
         -> __alloc_pages()

It does something with zones. Looks like zone memory
pages are locked in the beginning.
Still could not figure out the instuctions for page
locking.

quoted

   
  Can anybody tell me which instructions do we use

to set this page entry in TLB and page table?

quoted

  What bit gets set in the PTE for this?

Why do you need this page in TLB?

[Parav] No, I don't want. I just wanted to see the
code for locking inside TLB or in page table.

In general you don't have to worry about _any_
memory you allocated in 
the kernel to be paged out.

[Parav] As driver writer, I agree I don't need to, but
to better understand the system I am eager to do that.

Regards,
Parav


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