cbb/ata induces high interrupt load

[Paul Allen]

While performing a sequential read from a compact flash disk over
cardbus (cbb), I observe the following:

iostat reports transfer rate of 0.72MB/s with average transaction size of 32K
top -S reports 80% interrupt time. 78% of which is attributed to irq11

vmstat -i reports about an order of magnitude more interrupt load on irq11.

dmesg | grep 'irq 11' shows:

cbb0: <TI1450 PCI-CardBus Bridge> mem 0x50000000-0x50000fff irq 11 at device 2.0 on pci0
cbb1: <TI1450 PCI-CardBus Bridge> mem 0x50100000-0x50100fff irq 11 at device 2.1 on pci0
ata2: <SAMSUNG 04/05/06> at port 0x100-0x10f irq 11 function 0 config 1 on pccard1

Any suggestions?