Re: [RFC][PATCH 0/5] VM_PINNED

[Konstantin Khlebnikov]

On Mon, May 26, 2014 at 6:56 PM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> Hi all,
>
> I mentioned at LSF/MM that I wanted to revive this, and at the time there were
> no disagreements.
>
> I finally got around to refreshing the patch(es) so here goes.
>
> These patches introduce VM_PINNED infrastructure, vma tracking of persistent
> 'pinned' page ranges. Pinned is anything that has a fixed phys address (as
> required for say IO DMA engines) and thus cannot use the weaker VM_LOCKED. One
> popular way to pin pages is through get_user_pages() but that not nessecarily
> the only way.

Lol, this looks like resurrection of VM_RESERVED which I've removed
not so long time ago.

Maybe single-bit state isn't flexible enought?
This supposed to supports pinning only by one user and only in its own mm?

This might be done as extension of existing memory-policy engine.
It allows to keep vm_area_struct slim in normal cases and change
behaviour when needed.
memory-policy might hold reference-counter of "pinners", track
ownership and so on.

>
> Roland, as said, I need some IB assistance, see patches 4 and 5, where I got
> lost in the qib and ipath code.
>
> Patches 1-3 compile tested.
>
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