clock

type Counter ¶

type Counter struct {
	// contains filtered or unexported fields
}

A Counter converts the ticks of one queue's completions to nanoseconds, carrying the wraps.

The counter in a completion is narrow -- 41 bits on a ConnectX-6 Dx, which at a nanosecond a tick comes back round every 37 minutes -- so scaling it on its own gives a time that jumps backwards by half an hour several times a day, and one interval of about six hundred years each time it does. Anything watching a link for longer than half an hour meets this, and the whole point of a timestamp is the interval between two of them.

So the wraps are counted here and added back, which makes the result rise for as long as the queue is open. A Counter belongs to one queue and is not safe to share, like everything else on the receive path.

func New(i Info) *Counter

func (c *Counter) NS(ticks uint64) uint64

type Info ¶

type Info struct {
	Mult  uint32
	Shift uint32
	Mask  uint64
}

Info is how a device's timestamps convert, as the driver reports it: a duration is ticks * Mult >> Shift, and the counter is Mask bits wide.

func (i Info) OK() bool