On Mon, Jul 31, 2006 at 08:35:55PM +1000, Herbert Xu (herbert@gondor.apana.org.au) wrote:

Evgeniy Polyakov [off-list ref] wrote:

quoted

quoted

- if there is space, report it in the ring buffer.  Yes, the buffer
  can be optional, then all events are reported by the system call.

That requires a copy, which can neglect syscall overhead.
Do we really want it to be done?

Please note that we're talking about events here, not actual data.  So
only the event is being copied, which is presumably rather small compared
to the data.

In syscall time kevents copy 40bytes for each event + 12 bytes of header 
(number of events, timeout and command number). That's likely two cache
lines if only one event is reported.

-- 
	Evgeniy Polyakov