Re: [PATCH] cgroup/dmem: implement dmem.high soft limit and throttling

[Qiliang Yuan]

Hi Natalie,

On Thu, May 21, 2026 at 10:52 AM Natalie Vock wrote:
> Interesting proposal, but inserting sleeps on allocation is never a good 
> idea and doesn't work like you might think it does. In graphics driver 
> land, lots of random things may result in buffer allocation functions 
> being called. 
[...]
> Your approach could lead to every single 
> submission sleeping for at least 100ms, thus permanently destroying 
> performance.

Thank you very much for the detailed explanation of the impact on TTM and 
Submit IOCTLs. You are absolutely right—injecting sleeps into the charge 
path, which is hit frequently during buffer validation and residency changes, 
would indeed be catastrophic for GPU performance.

> Maarten's suggestion of preferentially evicting memory that is over the 
> high limit sounds like a better approach.

I agree. Blocking the submission pipeline is not the right way to apply 
backpressure. I will abandon the current sleep-on-allocation approach and 
focus on implemented prioritized eviction as you and Maarten suggested. 
This ensures that reaching the "high" limit triggers a meaningful reclaim 
action rather than just stalling the GPU pipeline.

Best regards,
Qiliang