[RFC] perf migration

[RFC] perf migration

[Frederic Weisbecker]

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Hi,

To begin with, the name is a bit pompous. It's not a strong
cpu task migration observer as it's only based on the
number of tasks living in a cpu runqueue. This is the only basis
for the cpu load: it doesn't handle the nice level, scheduler classes,
of each tasks (except idle ones that don't count on the load).

At least not yet.

But still I think it's a cool toy, I've been playing with it for
the last weeks and it can give you a nice overview of what happens
wrt migration decisions for each migration opportunities: wake up,
fork and exec, sleep (sleep doesn't involve migration decision,
but it's still an rq detach), and load balancing. In fact it's
more about "runqueue events".


== Layout ==


This is a classical cpu line based tracing GUI. Each CPU has a rectangle that
exposes the events in a rectangle.

The whole thing is based on timeslices. Each time a cpu get an rq migration
event (again: wake up, fork/exec, sleep, load balancing), then a new global
timeslice is built, materialized by a subrectangle inside each cpu rectangle.
Then each runqueue contents are compared for the given timeslice and the
subrectangles get a color attributed based on the number of tasks.

If CPU 0 has 2 tasks and CPU 1 has 1 task, the subrectangle in CPU 0 will
have a dark red (2/3 full red) and CPU 1 will have a lighter one (1/3 full red).

If a CPU is idle, its subrectangle for this timeslice will be white.

The cpu that got the event will have a thin colored line on the top of its
subrectangle that describes the runqueue event that happened:

yellow = a task woke up
dark blue = a task went to sleep
green = a new task woke up (fork)
light blue = tasks migrated in (load balancing)
violet = tasks migrated out (load balancing)

Usually the last two ones are paired.


If you click on the subrectangle timeslice, you'll get a description of
the runqueue event that happened: cpu, timestamp, duration until the next rq event
(should be renamed to "time remaining until the next rq event"), load (number of
tasks in the runqueue), and finally a dump of the tasks.

Example here: http://tglx.de/~fweisbec/migrate-example.png

I've just clicked on the first visible event in CPU 0. Both CPUs have equal load
(1 task) and the yellow thin line shows there has been a wake up event on CPU 0,
the description on the bottom describes which task has woken up and the various
other informations.

== Controls ==

There are classical controls from the mouse and keyboad. You can use left and right
arrow to navigate on the cpu rectangles, provided you have the focus on the top window.

And you can zoom in and out using the "+" and "-" buttons.


== Problems ==

I only have "two CPU" testboxes so you'll have problems to see rectangles if you
have more cpus. I have yet to make a vertical scrollable that works well for that.

If you bring the zoom too far, you'll have some issues with the display, I need
to put some limits there.

The bottom window also need to be scrollable, so that the task list of a runqueue is
entirely visible if there are too many of them.


== To be improved == 


It is still quite alpha. May be we can bring more modes that define the load (nice
levels, sched classes, etc...)

Amongst many other GUI improvements (I'm quite not used to write GUIs).


== How to use ==


I suggest you to use latest tip:/perf/core

Run the following command (followed by a command if you want):

$ sudo ./perf record -m 16384 -a -e sched:sched_wakeup -e sched:sched_wakeup_new -e sched:sched_switch -e sched:sched_migrate_task


Now ensure you have no lost events:


$ sudo ./perf trace -d
Misordered timestamps: 0
Lost events: 0 <----


If so you need to increase the buffer size (-m nr_pages option in perf record).

Then put the script in the tools/perf directory and run it:

$ ./perf trace -s migration.py

You'll need wxpython.

The script is in attachment.

Thanks.

[-- Attachment #2: migration.py --]
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#!/usr/bin/python
#
# Cpu task migration overview toy
#
# Copyright (C) 2010 Frederic Weisbecker <fweisbec@gmail.com>
#
# perf trace event handlers have been generated by perf trace -g python
#
# The whole is licensed under the terms of the GNU GPL License version 2


try:
	import wx
except ImportError:
	raise ImportError, "You need to install the wxpython lib for this script"

import os
import sys

from collections import defaultdict
from UserList import UserList

sys.path.append(os.environ['PERF_EXEC_PATH'] + \
	'/scripts/python/Perf-Trace-Util/lib/Perf/Trace')

from perf_trace_context import *
from Core import *

class RootFrame(wx.Frame):
	def __init__(self, timeslices, parent = None, id = -1, title = "Migration"):
		wx.Frame.__init__(self, parent, id, title)
		
		(self.screen_width, self.screen_height) = wx.GetDisplaySize()
		self.screen_width -= 10
		self.screen_height -= 10
		self.zoom = 0.5
		self.scroll_scale = 20
		self.timeslices = timeslices
		(self.ts_start, self.ts_end) = timeslices.interval()
		self.update_width_virtual()

		# whole window panel
		self.panel = wx.Panel(self, size=(self.screen_width, self.screen_height))

		# scrollable container
		self.scroll = wx.ScrolledWindow(self.panel)
		self.scroll.SetScrollbars(self.scroll_scale, self.scroll_scale, self.width_virtual / self.scroll_scale, 100 / 10)
		self.scroll.EnableScrolling(True, True)
		self.scroll.SetFocus()

		# scrollable drawing area
		self.scroll_panel = wx.Panel(self.scroll, size=(self.screen_width, self.screen_height / 2))
		self.scroll_panel.Bind(wx.EVT_PAINT, self.on_paint)
		self.scroll_panel.Bind(wx.EVT_KEY_DOWN, self.on_key_press)
		self.scroll_panel.Bind(wx.EVT_LEFT_DOWN, self.on_mouse_down)
		self.scroll.Bind(wx.EVT_PAINT, self.on_paint)

		self.scroll.Fit()
		self.Fit()

		self.scroll_panel.SetDimensions(-1, -1, self.width_virtual, -1, wx.SIZE_USE_EXISTING)

		self.max_cpu = -1
		self.txt = None

		self.Show(True)

	def us_to_px(self, val):
		return val / (10 ** 3) * self.zoom

	def px_to_us(self, val):
		return (val / self.zoom) * (10 ** 3)

	def scroll_start(self):
		(x, y) = self.scroll.GetViewStart()
		return (x * self.scroll_scale, y * self.scroll_scale)

	def scroll_start_us(self):
		(x, y) = self.scroll_start()
		return self.px_to_us(x)

	def update_rectangle_cpu(self, dc, slice, cpu, offset_time):
		rq = slice.rqs[cpu]

		if slice.total_load != 0:
			load_rate = rq.load() / float(slice.total_load)
		else:
			load_rate = 0

		
		offset_px = self.us_to_px(slice.start - offset_time)
		width_px = self.us_to_px(slice.end - slice.start)
		(x, y) = self.scroll_start()

		if width_px == 0:
			return

		offset_py = 100 + (cpu * 150)
		width_py = 100

		if cpu in slice.event_cpus:
			rgb = rq.event.color()
			if rgb is not None:
				(r, g, b) = rgb
				color = wx.Colour(r, g, b)
				brush = wx.Brush(color, wx.SOLID)
				dc.SetBrush(brush)
				dc.DrawRectangle(offset_px, offset_py, width_px, 5)
				width_py -= 5
				offset_py += 5

		red_power = int(0xff - (0xff * load_rate))
		color = wx.Colour(0xff, red_power, red_power)
		brush = wx.Brush(color, wx.SOLID)
		dc.SetBrush(brush)
		dc.DrawRectangle(offset_px, offset_py, width_px, width_py)

	def update_rectangles(self, dc, start, end):
		if len(self.timeslices) == 0:
			return
		start += self.timeslices[0].start
		end += self.timeslices[0].start

		color = wx.Colour(0, 0, 0)
		brush = wx.Brush(color, wx.SOLID)
		dc.SetBrush(brush)

		i = self.timeslices.find_time_slice(start)
		if i == -1:
			return

		for i in xrange(i, len(self.timeslices)):
			timeslice = self.timeslices[i]
			if timeslice.start > end:
				return

			for cpu in timeslice.rqs:
				self.update_rectangle_cpu(dc, timeslice, cpu, self.timeslices[0].start)
				if cpu > self.max_cpu:
					self.max_cpu = cpu

	def on_paint(self, event):
		color = wx.Colour(0xff, 0xff, 0xff)
		brush = wx.Brush(color, wx.SOLID)
		dc = wx.PaintDC(self.scroll_panel)
		dc.SetBrush(brush)
		
		width = min(self.width_virtual, self.screen_width)
		(x, y) = self.scroll_start()
		start = self.px_to_us(x)
		end = self.px_to_us(x + width)
		self.update_rectangles(dc, start, end)

	def cpu_from_ypixel(self, y):
		y -= 100
		cpu = y / 150
		height = y % 150

		if cpu < 0 or cpu > self.max_cpu or height > 100:
			return -1

		return cpu

	def update_summary(self, cpu, t):
		idx = self.timeslices.find_time_slice(t)
		if idx == -1:
			return

		ts = self.timeslices[idx]
		rq = ts.rqs[cpu]
		raw = "CPU: %d\n" % cpu
		raw += "Last event : %s\n" % rq.event.__repr__()
		raw += "Timestamp : %d.%06d\n" % (ts.start / (10 ** 9), (ts.start % (10 ** 9)) / 1000)
		raw += "Duration : %6d us\n" % ((ts.end - ts.start) / (10 ** 6))
		raw += "Load = %d\n" % rq.load()
		for t in rq.tasks:
			raw += "%s \n" % thread_name(t)

		if self.txt:
			self.txt.Destroy()
		self.txt = wx.StaticText(self.panel, -1, raw, (0, (self.screen_height / 2) + 50))
		

	def on_mouse_down(self, event):
		(x, y) = event.GetPositionTuple()
		cpu = self.cpu_from_ypixel(y)
		if cpu == -1:
			return

		t = self.px_to_us(x) + self.timeslices[0].start

		self.update_summary(cpu, t)
		

	def update_width_virtual(self):
		self.width_virtual = self.us_to_px(self.ts_end - self.ts_start)

	def __zoom(self, x):
		self.update_width_virtual()
		(xpos, ypos) = self.scroll.GetViewStart()
		xpos = self.us_to_px(x) / self.scroll_scale
		self.scroll.SetScrollbars(self.scroll_scale, self.scroll_scale, self.width_virtual / self.scroll_scale, 100 / 10, xpos, ypos)
		self.Refresh()

	def zoom_in(self):
		x = self.scroll_start_us()
		self.zoom *= 2
		self.__zoom(x)

	def zoom_out(self):
		x = self.scroll_start_us()
		self.zoom /= 2
		self.__zoom(x)
		

	def on_key_press(self, event):
		key = event.GetRawKeyCode()
		if key == ord("+"):
			self.zoom_in()
			return
		if key == ord("-"):
			self.zoom_out()
			return

		key = event.GetKeyCode()
		(x, y) = self.scroll.GetViewStart()
		if key == wx.WXK_RIGHT:
			self.scroll.Scroll(x + 1, y)
		elif key == wx.WXK_LEFT:
			self.scroll.Scroll(x -1, y)


threads = { 0 : "idle"}

def thread_name(pid):
	return "%s:%d" % (threads[pid], pid)

class EventHeaders:
	def __init__(self, common_cpu, common_secs, common_nsecs,
		     common_pid, common_comm):
		self.cpu = common_cpu
		self.secs = common_secs
		self.nsecs = common_nsecs
		self.pid = common_pid
		self.comm = common_comm

	def ts(self):
		return (self.secs * (10 ** 9)) + self.nsecs

	def ts_format(self):
		return "%d.%d" % (self.secs, int(self.nsecs / 1000))


def taskState(state):
	states = {
		0 : "R",
		1 : "S",
		2 : "D",
		64: "DEAD"
	}

	if state not in states:
		print "Unhandled task state %d" % state
		return ""

	return states[state]


class RunqueueEventUnknown:
	@staticmethod
	def color():
		return None

	def __repr__(self):
		return "unknown"

class RunqueueEventSleep:
	@staticmethod
	def color():
		return (0, 0, 0xff)

	def __init__(self, sleeper):
		self.sleeper = sleeper

	def __repr__(self):
		return "%s gone to sleep" % thread_name(self.sleeper)

class RunqueueEventWakeup:
	@staticmethod
	def color():
		return (0xff, 0xff, 0)

	def __init__(self, wakee):
		self.wakee = wakee

	def __repr__(self):
		return "%s woke up" % thread_name(self.wakee)

class RunqueueEventFork:
	@staticmethod
	def color():
		return (0, 0xff, 0)

	def __init__(self, child):
		self.child = child

	def __repr__(self):
		return "new forked task %s" % thread_name(self.child)

class RunqueueMigrateIn:
	@staticmethod
	def color():
		return (0, 0xf0, 0xff)

	def __init__(self, new):
		self.new = new

	def __repr__(self):
		return "task migrated in %s" % thread_name(self.new)

class RunqueueMigrateOut:
	@staticmethod
	def color():
		return (0xff, 0, 0xff)

	def __init__(self, old):
		self.old = old

	def __repr__(self):
		return "task migrated out %s" % thread_name(self.old)

class RunqueueSnapshot:
	def __init__(self, tasks = [0], event = RunqueueEventUnknown()):
		self.tasks = tuple(tasks)
		self.event = event

	def sched_switch(self, prev, prev_state, next):
		event = RunqueueEventUnknown()

		if taskState(prev_state) == "R" and next in self.tasks \
			and prev in self.tasks:
			return self

		if taskState(prev_state) != "R":
			event = RunqueueEventSleep(prev)

		next_tasks = list(self.tasks[:])
		if prev in self.tasks:
			if taskState(prev_state) != "R":
				next_tasks.remove(prev)
		elif taskState(prev_state) == "R":
			next_tasks.append(prev)
			
		if next not in next_tasks:
			next_tasks.append(next)

		return RunqueueSnapshot(next_tasks, event)

	def migrate_out(self, old):
		if old not in self.tasks:
			return self
		next_tasks = [task for task in self.tasks if task != old]

		return RunqueueSnapshot(next_tasks, RunqueueMigrateOut(old))

	def __migrate_in(self, new, event):
		if new in self.tasks:
			self.event = event
			return self
		next_tasks = self.tasks[:] + tuple([new])

		return RunqueueSnapshot(next_tasks, event)

	def migrate_in(self, new):
		return self.__migrate_in(new, RunqueueMigrateIn(new))

	def wake_up(self, new):
		return self.__migrate_in(new, RunqueueEventWakeup(new))

	def wake_up_new(self, new):
		return self.__migrate_in(new, RunqueueEventFork(new))

	def load(self):
		""" Provide the number of tasks on the runqueue.
		    Don't count idle"""
		return len(self.tasks) - 1

	def __repr__(self):
		ret = self.tasks.__repr__()
		ret += self.origin_tostring()

		return ret

class TimeSlice:
	def __init__(self, start, prev):
		self.start = start
		self.prev = prev
		self.end = start
		# cpus that triggered the event
		self.event_cpus = []
		if prev is not None:
			self.total_load = prev.total_load
			self.rqs = prev.rqs.copy()
		else:
			self.rqs = defaultdict(RunqueueSnapshot)
			self.total_load = 0

	def __update_total_load(self, old_rq, new_rq):
		diff = new_rq.load() - old_rq.load()
		self.total_load += diff
		
	def sched_switch(self, ts_list, prev, prev_state, next, cpu):
		old_rq = self.prev.rqs[cpu]
		new_rq = old_rq.sched_switch(prev, prev_state, next)
		
		if old_rq is new_rq:
			return

		self.rqs[cpu] = new_rq
		self.__update_total_load(old_rq, new_rq)
		ts_list.append(self)
		self.event_cpus = [cpu]

	def migrate(self, ts_list, new, old_cpu, new_cpu):
		if old_cpu == new_cpu:
			return
		old_rq = self.prev.rqs[old_cpu]
		out_rq = old_rq.migrate_out(new)
		self.rqs[old_cpu] = out_rq
		self.__update_total_load(old_rq, out_rq)

		new_rq = self.prev.rqs[new_cpu]
		in_rq = new_rq.migrate_in(new)
		self.rqs[new_cpu] = in_rq
		self.__update_total_load(new_rq, in_rq)

		ts_list.append(self)
		self.event_cpus = [old_cpu, new_cpu]

	def wake_up(self, ts_list, pid, cpu, fork):
		old_rq = self.prev.rqs[cpu]
		if fork:
			new_rq = old_rq.wake_up_new(pid)
		else:
			new_rq = old_rq.wake_up(pid)

		if new_rq is old_rq:
			return
		self.rqs[cpu] = new_rq
		self.__update_total_load(old_rq, new_rq)
		ts_list.append(self)
		self.event_cpus = [cpu]

	def next(self, t):
		self.end = t
		return TimeSlice(t, self)

class TimeSliceList(UserList):
	def __init__(self, arg = []):
		self.data = arg

	def get_time_slice(self, ts):
		if len(self.data) == 0:
			slice = TimeSlice(ts, TimeSlice(-1, None))
		else:
			slice = self.data[-1].next(ts)
		return slice

	def find_time_slice(self, ts):
		start = 0
		end = len(self.data)
		found = -1
		searching = True
		while searching:
			if start == end or start == end - 1:
				searching = False

			i = (end + start) / 2
			if self.data[i].start <= ts and self.data[i].end >= ts:
				found = i
				end = i
				continue

			if self.data[i].end < ts:
				start = i

			elif self.data[i].start > ts:
				end = i

		return found

	def interval(self):
		if len(self.data) == 0:
			return (0, 0)

		return (self.data[0].start, self.data[-1].end)


class SchedEventProxy:
	def __init__(self):
		self.current_tsk = defaultdict(lambda : -1)
		self.timeslices = TimeSliceList()

	def sched_switch(self, headers, prev_comm, prev_pid, prev_prio, prev_state, 
			 next_comm, next_pid, next_prio):
		""" Ensure the task we sched out this cpu is really the one
		    we logged. Otherwise we may have missed traces """

		on_cpu_task = self.current_tsk[headers.cpu]

		if on_cpu_task != -1 and on_cpu_task != prev_pid:
			print "Sched switch event rejected ts: %s cpu: %d prev: %s(%d) next: %s(%d)" % \
				(headers.ts_format(), headers.cpu, prev_comm, prev_pid, next_comm, next_pid)

		threads[prev_pid] = prev_comm
		threads[next_pid] = next_comm
		self.current_tsk[headers.cpu] = next_pid

		ts = self.timeslices.get_time_slice(headers.ts())
		ts.sched_switch(self.timeslices, prev_pid, prev_state, next_pid, headers.cpu)

	def migrate(self, headers, pid, prio, orig_cpu, dest_cpu):
		ts = self.timeslices.get_time_slice(headers.ts())
		ts.migrate(self.timeslices, pid, orig_cpu, dest_cpu)

	def wake_up(self, headers, comm, pid, success, target_cpu, fork):
		if success == 0:
			return
		ts = self.timeslices.get_time_slice(headers.ts())
		ts.wake_up(self.timeslices, pid, target_cpu, fork)


def trace_begin():
	global parser
	parser = SchedEventProxy()

def trace_end():
	app = wx.App(False)
	timeslices = parser.timeslices
	frame = RootFrame(timeslices)
	app.MainLoop()

def sched__sched_stat_runtime(event_name, context, common_cpu,
	common_secs, common_nsecs, common_pid, common_comm,
	comm, pid, runtime, vruntime):
	pass

def sched__sched_stat_iowait(event_name, context, common_cpu,
	common_secs, common_nsecs, common_pid, common_comm,
	comm, pid, delay):
	pass

def sched__sched_stat_sleep(event_name, context, common_cpu,
	common_secs, common_nsecs, common_pid, common_comm,
	comm, pid, delay):
	pass

def sched__sched_stat_wait(event_name, context, common_cpu,
	common_secs, common_nsecs, common_pid, common_comm,
	comm, pid, delay):
	pass

def sched__sched_process_fork(event_name, context, common_cpu,
	common_secs, common_nsecs, common_pid, common_comm,
	parent_comm, parent_pid, child_comm, child_pid):
	pass

def sched__sched_process_wait(event_name, context, common_cpu,
	common_secs, common_nsecs, common_pid, common_comm,
	comm, pid, prio):
	pass

def sched__sched_process_exit(event_name, context, common_cpu,
	common_secs, common_nsecs, common_pid, common_comm,
	comm, pid, prio):
	pass

def sched__sched_process_free(event_name, context, common_cpu,
	common_secs, common_nsecs, common_pid, common_comm,
	comm, pid, prio):
	pass

def sched__sched_migrate_task(event_name, context, common_cpu,
	common_secs, common_nsecs, common_pid, common_comm,
	comm, pid, prio, orig_cpu, 
	dest_cpu):
	headers = EventHeaders(common_cpu, common_secs, common_nsecs,
				common_pid, common_comm)
	parser.migrate(headers, pid, prio, orig_cpu, dest_cpu)

def sched__sched_switch(event_name, context, common_cpu,
	common_secs, common_nsecs, common_pid, common_comm,
	prev_comm, prev_pid, prev_prio, prev_state, 
	next_comm, next_pid, next_prio):

	headers = EventHeaders(common_cpu, common_secs, common_nsecs,
				common_pid, common_comm)
	parser.sched_switch(headers, prev_comm, prev_pid, prev_prio, prev_state, 
			 next_comm, next_pid, next_prio)

def sched__sched_wakeup_new(event_name, context, common_cpu,
	common_secs, common_nsecs, common_pid, common_comm,
	comm, pid, prio, success, 
	target_cpu):
	headers = EventHeaders(common_cpu, common_secs, common_nsecs,
				common_pid, common_comm)
	parser.wake_up(headers, comm, pid, success, target_cpu, 1)

def sched__sched_wakeup(event_name, context, common_cpu,
	common_secs, common_nsecs, common_pid, common_comm,
	comm, pid, prio, success, 
	target_cpu):
	headers = EventHeaders(common_cpu, common_secs, common_nsecs,
				common_pid, common_comm)
	parser.wake_up(headers, comm, pid, success, target_cpu, 0)

def sched__sched_wait_task(event_name, context, common_cpu,
	common_secs, common_nsecs, common_pid, common_comm,
	comm, pid, prio):
	pass

def sched__sched_kthread_stop_ret(event_name, context, common_cpu,
	common_secs, common_nsecs, common_pid, common_comm,
	ret):
	pass

def sched__sched_kthread_stop(event_name, context, common_cpu,
	common_secs, common_nsecs, common_pid, common_comm,
	comm, pid):
	pass

def trace_unhandled(event_name, context, common_cpu, common_secs, common_nsecs,
		common_pid, common_comm):
	pass

Re: [RFC] perf migration

[Ingo Molnar]

* Frederic Weisbecker <fweisbec@gmail.com> wrote:

> Hi,
> 
> To begin with, the name is a bit pompous. It's not a strong cpu task 
> migration observer as it's only based on the number of tasks living in a cpu 
> runqueue. This is the only basis for the cpu load: it doesn't handle the 
> nice level, scheduler classes, of each tasks (except idle ones that don't 
> count on the load).
> 
> At least not yet.
> 
> But still I think it's a cool toy, I've been playing with it for the last 
> weeks and it can give you a nice overview of what happens wrt migration 
> decisions for each migration opportunities: wake up, fork and exec, sleep 
> (sleep doesn't involve migration decision, but it's still an rq detach), and 
> load balancing. In fact it's more about "runqueue events".

Cool, looks really nice!

> == How to use ==
> 
> 
> I suggest you to use latest tip:/perf/core
> 
> Run the following command (followed by a command if you want):
> 
> $ sudo ./perf record -m 16384 -a -e sched:sched_wakeup -e sched:sched_wakeup_new -e sched:sched_switch -e sched:sched_migrate_task

Does 'perf sched record' include these events?

> Now ensure you have no lost events:
> 
> 
> $ sudo ./perf trace -d
> Misordered timestamps: 0
> Lost events: 0 <----

We need some warning for this in the GUI i guess?

> If so you need to increase the buffer size (-m nr_pages option in perf record).
> 
> Then put the script in the tools/perf directory and run it:
> 
> $ ./perf trace -s migration.py
> 
> You'll need wxpython.

Looks like this could be turned into 'perf sched view' or 'perf sched 
migration'?

How tasks schedule/migrate is basically how scheduler developers look at 
sched-trace data, so it would be nice if your GUI became the gui for perf 
sched.

	Ingo

Re: [RFC] perf migration

[Frederic Weisbecker]

On Thu, Jul 08, 2010 at 09:19:42AM +0200, Ingo Molnar wrote:
> 
> * Frederic Weisbecker <fweisbec@gmail.com> wrote:
> 
> > Hi,
> > 
> > To begin with, the name is a bit pompous. It's not a strong cpu task 
> > migration observer as it's only based on the number of tasks living in a cpu 
> > runqueue. This is the only basis for the cpu load: it doesn't handle the 
> > nice level, scheduler classes, of each tasks (except idle ones that don't 
> > count on the load).
> > 
> > At least not yet.
> > 
> > But still I think it's a cool toy, I've been playing with it for the last 
> > weeks and it can give you a nice overview of what happens wrt migration 
> > decisions for each migration opportunities: wake up, fork and exec, sleep 
> > (sleep doesn't involve migration decision, but it's still an rq detach), and 
> > load balancing. In fact it's more about "runqueue events".
> 
> Cool, looks really nice!
> 
> > == How to use ==
> > 
> > 
> > I suggest you to use latest tip:/perf/core
> > 
> > Run the following command (followed by a command if you want):
> > 
> > $ sudo ./perf record -m 16384 -a -e sched:sched_wakeup -e sched:sched_wakeup_new -e sched:sched_switch -e sched:sched_migrate_task
> 
> Does 'perf sched record' include these events?



Yeah. In fact it would include too much by adding traces you don't need, so there
are more risks to lose traces while using perf sched record.



 
> > Now ensure you have no lost events:
> > 
> > 
> > $ sudo ./perf trace -d
> > Misordered timestamps: 0
> > Lost events: 0 <----
> 
> We need some warning for this in the GUI i guess?



Yeah. In fact we need to add that from the tracing/scripting layer
and always check/report lost events to the user.



> > If so you need to increase the buffer size (-m nr_pages option in perf record).
> > 
> > Then put the script in the tools/perf directory and run it:
> > 
> > $ ./perf trace -s migration.py
> > 
> > You'll need wxpython.
> 
> Looks like this could be turned into 'perf sched view' or 'perf sched 
> migration'?
> 
> How tasks schedule/migrate is basically how scheduler developers look at 
> sched-trace data, so it would be nice if your GUI became the gui for perf 
> sched.
> 
> 	Ingo



Agreed. For now it's very tied to the cpu load idea, so the code needs to
be generalized to easily plug other sched drawing plugins. But yeah, that would
be indeed a good direction.