Jesse Brandeburg wrote:
included netdev...
On 11/8/06, Jeff V. Merkey <[email protected]> wrote:
Is there a good reason the skb refill routine in e1000_alloc_rx_buffers
needs to go and touch and remap skb memory
on already loaded descriptors/ This seems extremely wasteful of
processor cycles when refilling the ring buffer.
I note that the archtiecture has changed and is recycling buffers from
the rx_irq routine and when the routine is called
to refill the ring buffers, a lot of wasteful and needless calls for
map_skb is occurring.
we have to unmap the descriptor (or at least do
pci_dma_sync_single_for_cpu / pci_dma_sync_single_for_device) because
the dma API says we can't be guaranteed the cacheable memory is
consistent until we do one of the afore mentioned pci dma ops.
In the case I am referring to, the memory is already mapped with a
previous call, which means it may be getting
mapped twice.
Jeff
we have to do *something* before we access it. Simplest path is to
unmap it and then recycle/map it.
If you can show that it is faster to use pci_dma_sync_single_for_cpu
and friends I'd be glad to take a patch.
Hope this helps,
Jesse
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