Re: Running DPDK as an unprivileged user

[Thomas Monjalon <thomas@monjalon.net>]

Hi, restarting an old topic,

05/01/2017 16:52, Tan, Jianfeng:
> On 1/5/2017 5:34 AM, Walker, Benjamin wrote:
> >>> Note that this
> >>> probably means that using uio on recent kernels is subtly
> >>> broken and cannot be supported going forward because there
> >>> is no uio mechanism to pin the memory.
> >>>
> >>> The first open question I have is whether DPDK should allow
> >>> uio at all on recent (4.x) kernels. My current understanding
> >>> is that there is no way to pin memory and hugepages can now
> >>> be moved around, so uio would be unsafe. What does the
> >>> community think here?
> 
> Back to this question, removing uio support in DPDK seems a little 
> overkill to me. Can we just document it down? Like, firstly warn users 
> do not invoke migrate_pages() or move_pages() to a DPDK process; as for 
> the kcompactd daemon and some more cases (like compaction could be 
> triggered by alloc_pages()), could we just recommend to disable 
> CONFIG_COMPACTION?

We really need to better document the limitations of UIO.
May we have some suggestions here?

> Another side, how does vfio pin those memory? Through memlock (from code 
> in vfio_pin_pages())? So why not just mlock those hugepages?

Good question. Why not mlock the hugepages?