On Thu, Apr 22, 2021 at 04:19:16PM +0800, Jason Wang wrote: > > 在 2021/4/22 下午2:31, Christoph Hellwig 写道: > > On Wed, Apr 21, 2021 at 11:21:10AM +0800, Jason Wang wrote: > > > The behaivor for non DMA API is kept for minimizing the performance > > > impact. > > NAK. Everyone should be using the DMA API in a modern world. So > > treating the DMA API path worse than the broken legacy path does not > > make any sense whatsoever. > > > I think the goal is not treat DMA API path worse than legacy. The issue is > that the management layer should guarantee that ACCESS_PLATFORM is set so > DMA API is guaranteed to be used by the driver. So I'm not sure how much > value we can gain from trying to 'fix' the legacy path. But I can change the > behavior of legacy path to match DMA API path. > > Thanks I think before we maintain different paths with/without ACCESS_PLATFORM it's worth checking whether it's even a net gain. Avoiding sharing by storing data in private memory can actually turn out to be a net gain even without DMA API. It is worth checking what is the performance effect of this patch. -- MST
