On Wed, Jan 11, 2017 at 04:08:31PM +0000, Bart Van Assche wrote:

[...]

A typical Ethernet network adapter delays the generation of an interrupt
after it has received a packet. A typical block device or HBA does not delay
the generation of an interrupt that reports an I/O completion. I think that
is why polling is more effective for network adapters than for block
devices. I'm not sure whether it is possible to achieve benefits similar to
NAPI for block devices without implementing interrupt coalescing in the
block device firmware. Note: for block device implementations that use the
RDMA API, the RDMA API supports interrupt coalescing (see also
ib_modify_cq()).

Well you can always turn off IRQ generation in the HBA just before scheuduling
the poll handler and re-enable it after you've exhausted your budget or used
too much time, can't you? 

I'll do some prototyping and tests tomorrow so we have some more ground for
discussion.

Byte,
	Johannes
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Johannes Thumshirn                                          Storage
jthumshirn@suse.de                                +49 911 74053 689
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