# Re: \[RFC PATCH v3 1/2\] mempinfd: Add new syscall to provide memory pin

- From: Jason Gunthorpe \<jgg@ziepe.ca\>
- Date: 2021-02-10 18:15:46 
- List: linux-arm-kernel
- Page: https://ratatoskr.run/linux-arm-kernel/2021/02/6266269
- Thread: https://ratatoskr.run/linux-mm/2021/02/6261457/t.md

```text
On Tue, Feb 09, 2021 at 10:22:47PM +0000, Song Bao Hua (Barry Song) wrote:

> The problem is that SVA declares we can use any memory of a process
> to do I/O. And in real scenarios, we are unable to customize most
> applications to make them use the pool. So we are looking for some
> extension generically for applications such as Nginx, Ceph.

But those applications will suffer jitter even if their are using CPU
to do the same work. I fail to see why adding an accelerator suddenly
means the application owner will care about jitter introduced by
migration/etc.

Again in proper SVA it should be quite unlikely to take a fault caused
by something like migration, on the same likelyhood as the CPU. If
things are faulting so much this is a problem then I think it is a
system level problem with doing too much page motion.

Jason

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```