Re: [PATCH 1/8] mm: cma: introduce cma_release_nowait()

[Michal Hocko]

On Fri 26-03-21 14:32:01, Mike Kravetz wrote:
[...]
> - Just change the mutex to an irq safe spinlock.

Yes please.

>   AFAICT, the potential
>   downsides could be:
>   - Interrupts disabled during long bitmap scans

How large those bitmaps are in practice?

>   - Wasted cpu cycles (spinning) if there is much contention on lock
>   Both of these would be more of an issue on small/embedded systems. I
>   took a quick look at the callers of cma_alloc/cma_release and nothing
>   stood out that could lead to high degrees of contention.  However, I
>   could have missed something.

If this is really a practical concern then we can try a more complex
solution based on some data.

-- 
Michal Hocko
SUSE Labs