On 12/29/2017 11:50 AM, Christoph Hellwig wrote:
On Thu, Dec 21, 2017 at 02:34:00PM -0700, Keith Busch wrote:
It would be nice, but the driver doesn't know a request's completion
is going to be a polled.
We can trivially set a REQ_POLL bit. In fact my initial patch kit had
those on the insitence of Jens, but then I removed it because we had
no users for it.
Even if it did, we don't have a spec defined
way to tell the controller not to send an interrupt with this command's
compeletion, which would be negated anyway if any interrupt driven IO
is mixed in the same queue.
Time to add such a flag to the spec then..
That would be very useful, ideally we can also hook it into libaio
to submit without triggering an interrupt and have io_getevents to poll
the underlying bdev (blk_poll) similar to how the net stack implements
low latency sockets [1].
Having the ability to suppress interrupts and poll for completions would
be very useful for file servers or targets living in userspace.
https://lwn.net/Articles/551284/
