Messages in this thread | | | Date | Thu, 6 Aug 2020 07:18:14 +0200 | From | Christoph Hellwig <> | Subject | Re: [PATCH v2 2/2] dma-pool: Only allocate from CMA when in same memory zone |
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On Tue, Aug 04, 2020 at 11:43:15AM +0200, Nicolas Saenz Julienne wrote: > > Second I don't see the need (and actually some harm) in preventing GFP_KERNEL > > allocations from dipping into lower CMA areas - something that we did support > > before 5.8 with the single pool. > > My thinking is the least we pressure CMA the better, it's generally scarse, and > it'll not grow as the atomic pools grow. As far as harm is concerned, we now > check addresses for correctness, so we shouldn't run into problems. > > There is a potential case for architectures defining a default CMA but not > defining DMA zones where this could be problematic. But isn't that just plain > abusing CMA? If you need low memory allocations, you should be defining DMA > zones.
The latter is pretty much what I expect, as we only support the default and per-device DMA CMAs.
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