>> I think the issue at hand is whether, longer term, it is
>> desirable to move all bounce buffer handling into the PCI DMA
>> layer or whether Linux should continue to make bounce buffer
>> management visible to drivers. I'd be interested in hearing
>> opinions.
Alan> I think the performance figures we see currently answer that
Alan> already.
The numbers I have seen so far don't make this obvious. Tony Luck
reports 95Mbps with a CPU load of 20% after a fixing a performance bug
in the software I/O TLB. Arjan reported the same 95Mbps figure with
the highmem approach. Arjan didn't report the CPU load and neither
Tony nor Arjan specified the test environment they were using.
Alan> IA64 also needs to correct its GFP_DMA to mean "low 16Mb" for
Alan> ISA DMA. While there is no ISA DMA on ia64 (thankfully) many
Alan> PCI cards have 26-31 bit limits.
We could do this if we there was a GFP_4GB zone. Now that 2.5 is open
for business, it won't be long, right?
--david
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