On Wed, 8 Apr 2020 14:21:06 -0700 (PDT) David Rientjes wrote:
> 
> When an atomic pool becomes fully depleted because it is now relied upon
> for all non-blocking allocations through the DMA API, allow background
> expansion of each pool by a kworker.
> 
> When an atomic pool has less than the default size of memory left, kick
> off a kworker to dynamically expand the pool in the background.  The pool
> is doubled in size, up to MAX_ORDER-1.  If memory cannot be allocated at
> the requested order, smaller allocation(s) are attempted.
> 
What is proposed looks like a path of single lane without how to
dynamically shrink the pool taken into account. Thus the risk may
rise in corner cases where pools are over-expanded in long run
after one-off peak allocation requests.

Is it worth the complexity of expander + shrinker at the first place?

> This allows the default size to be kept quite low when one or more of the
> atomic pools is not used.
> 
> This also allows __dma_atomic_pool_init to return a pointer to the pool
> to make initialization cleaner.
> 
> Also switch over some node ids to the more appropriate NUMA_NO_NODE.

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