Provided by: systemtap-doc_2.3-1ubuntu1.4_all 

NAME
probe::ioscheduler_trace.unplug_io - Fires when a request queue is unplugged;
SYNOPSIS
ioscheduler_trace.unplug_io
VALUES
name
Name of the probe point
rq_queue
request queue
DESCRIPTION
Either, when number of pending requests in the queue exceeds threshold or, upon expiration of timer that
was activated when queue was plugged.
SystemTap Tapset Reference March 2016 PROBE::IOSCHEDULER_T(3stap)