[PATCH 0/5] prevent OOM triggered by TTM

[Thomas Hellstrom]

Hi, Roger,

On 02/06/2018 10:04 AM, Roger He wrote:
> currently ttm code has no any allocation limit. So it allows pages
> allocatation unlimited until OOM. Because if swap space is full
> of swapped pages and then system memory will be filled up with ttm
> pages. and then any memory allocation request will trigger OOM.
>

I'm a bit curious, isn't this the way things are supposed to work on a 
linux system?
If all memory resources are used up, the OOM killer will kill the most 
memory hungry (perhaps rogue) process
rather than processes being nice and try to find out themselves whether 
allocations will succeed?
Why should TTM be different in that aspect? It would be good to know 
your reasoning WRT this?

Admittedly, graphics process OOM memory accounting doesn't work very 
well, due to not all BOs not being
CPU mapped, but it looks like there is recent work towards fixing this?

One thing I looked at at one point was to have TTM do the swapping 
itself instead of handing it off to the
shmem system. That way we could pre-allocate swap entries for all 
swappable (BO) memory, making sure that
we wouldn't run out of swap space when, for example, hibernating and 
that would also limit the pinned
non-swappable memory (from TTM driver kernel allocations for example) to 
half the system memory resources.

Thanks,
Thomas