Messages in this thread | | | From | Benjamin Herrenschmidt <> | Subject | Re: PCI DMA to small buffers on cache-incoherent arch | Date | Tue, 11 Jun 2002 19:33:47 +0200 |
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>Remember please that specifically the DMA mapping APIs encourage use >of consistent memory for small data objects. It is specifically >because non-consistent DMA accesses to small bits are going to be very >slow (ie. the PCI controller is going to prefetch further cache lines >for no reason, for example). The non-consistent end of the APIs is >meant for long contiguous buffers, not small chunks. > >This is one of the reasons I want to fix this by making people use >either consistent memory or PCI pools (which is consistent memory >too).
Please don't limit the API design to PCI ;)
There are more and more embedded CPUs out there with their own bunch of on-chip devices that are neither consistent nor PCI based, their drivers will have the exact same problem to deal with though.
Ben.
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