On 3/29/21 12:46 AM, Michal Hocko wrote: > 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. > Ok, I will send v2 with this approach. Adding Barry and Will on Cc: as they were involved in adding more cma use cases for dma on arm. -- Mike Kravetz
