Messages in this thread | | | Subject | Re: Linux and real device drivers | From | Jes Sorensen <> | Date | 22 Sep 1999 14:41:28 +0200 |
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>>>>> "Momchil" == Momchil Velikov <velco@fadata.bg> writes:
Momchil> Alan Cox wrote: >> There is the jump/return overhead. There is the stack management >> overhead There is an extra cache line touched.
Momchil> Ok, folks, I think we are talking about "udi_pio_trans" call Momchil> (in UDI Physical I/O Specification) and this call is surely Momchil> not meant to perform a single I/O port or MMIO Momchil> read/write. Instead the UDI implementation executes a large Momchil> transaction including many reads, writes, arithmetic Momchil> operations, branches, etc. Now, the overhead is by no means Momchil> in the call, it's in interpreting the transaction description Momchil> and I'd say yes, it ought to be rather big.
No, for Gigabit Ethernet I have to do some 5-10 read/writes per packet to PCI shared memory, however these are not all one large block and go to different places in the PCI shared mem area. Most of this will have to be done with multiple UDI calls, unless they came up with a scatter/gather type list for this .... yuck.
Jes
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