Re: [RFC] mmap(MAP_CONTIG)

On 10/04/2017 09:05 AM, Christopher Lameter wrote:

On Wed, 4 Oct 2017, Anshuman Khandual wrote:

quoted

quoted

- Using 'pre-allocated' pages in the fault paths may be intrusive.

But we have already faulted in all of them for the mapping and they
are also locked. Hence there should not be any page faults any more
for the VMA. Am I missing something here ?

The PTEs may be torn down and have to reestablished through a page faults.
Page faults would not allocate memory.

quoted

I am still wondering why wait till fault time not pre fault all of them
and populate the page tables.

They are populated but some processes (swap and migration) may tear them
down.

As mentioned in my reply to Anshuman, the mention of fault paths here
may be a source of confusion.  I would expect the entire mapping to be
populated at mmap time, and the pages locked.  Therefore, there should
be no swap or migration.

-- 
Mike Kravetz

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