Re: [PATCHv2 0/2] remap_file_pages() decommission

[Konstantin Khlebnikov]

On Mon, May 12, 2014 at 7:36 AM, Andi Kleen <andi@xxxxxxxxxxxxxx> wrote:
> Armin Rigo <arigo@xxxxxxxxx> writes:
>
>> Here is a note from the PyPy project (mentioned earlier in this
>> thread, and at https://lwn.net/Articles/587923/ ).
>
> Your use is completely bogus. remap_file_pages() pins everything
> and disables any swapping for the area.

Wait, what's wrong with swapping pages from non-linear vmas?
try_to_umap() can handle them, though not very effectively.

Some time ago I was thinking about tracking rmap for non-linear vmas, something
like second-level tree of sub-vmas stored in non-linear vma. This
could be done using
exising vm_area_struct, and in rmap tree everything will looks just as normal.
We'll waste some kernel memory, but it also will remove complexity from rmap and
make non-linear vmas usable for all filesystems not just for shmem.

But it's not worth. I ACK killing it.

Maybe we should keep flag on vma and hide/merge them in proc/maps.
Bloating files/dirs in proc might be bigger problem than non-existent
performance regression.

>
> -Andi
> --
> ak@xxxxxxxxxxxxxxx -- Speaking for myself only
>
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