This only works if there is no significant drift and all processors are
running at the same frequency. Fortunately, schedgraph traces on MP
machines tend to cover less than a second so drift shouldn't be an issue.
- KTRFile::synchstamp() iterates once over the whole list to determine the
lowest tsc value and syncs adjusts all other values to match. We assume
that the first tick recorded on all cpus happened at the same instant to
start with.
- KTRFile::monostamp() iterates again over the whole file and checks for
a cpu agnostic monotonically increasing clock. If the time ever goes
backwards the cpu responsible is adjusted further to fit. This will
make the possible incorrect delta between cpus as small as the shortest
time between two events. This time can be fairly large due to sched_lock
essentially protecting all events.
- KTRFile::checkstamp() now returns an adjusted timestamp.
- StateEvent::draw() detects states that occur out of order in time and
draws them as 0 pixels after printing a warning.
from the tsc.
- Set skipnext = 1 for yielding and preempted events so we don't show the
event that adds us back to the run queue. It used to be 2 so we would
skip the ksegrp run queue addition and the system run queue addition
but the ksegrp run queue has gone away.
- Don't display down to nanosecond resolution for scheduling events right
now. This can sometimes cause a division by zero.
as they are the setrunqueue() and sched_add() calls. Since they happen
immediately before the thread is placed on a run queue they would normally
dwarf the more informative preemption or yield event and it is implicitly
understood that a thread is back on the run queue as part of these events.
python and tkinter. Schedgraph takes input from files produces by
ktrdump -ct when KTR_SCHED is compiled into the kernel. The output
represents the states of each thread with colored line segments as well
as colored points for non-state scheduler events. Each line segment and
point is clickable to obtain extra detail.
