perf script: Add drop monitor script

A while back I created the dropmonitor protocol, which allowed users to get
reports of dropped frames communicated to them via a netlink socket.

While useful, several people have now asked that I integrate the ability
to do drop monitoring with perf, so they don't have to run additional
tools.

This patch adds a drop monitor script to the perf suite, and provides
the same output that the netlink socket does.

Cc: Ingo Molnar <mingo@elte.hu>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1309801217-22450-1-git-send-email-nhorman@tuxdriver.com
Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/scripts/python/bin/net_dropmonitor-record

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+#!/bin/bash
+perf record -e skb:kfree_skb $@

tools/perf/scripts/python/bin/net_dropmonitor-report

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+#!/bin/bash
+# description: display a table of dropped frames
+
+perf script -s "$PERF_EXEC_PATH"/scripts/python/net_dropmonitor.py $@

tools/perf/scripts/python/net_dropmonitor.py

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+# Monitor the system for dropped packets and proudce a report of drop locations and counts
+
+import os
+import sys
+
+sys.path.append(os.environ['PERF_EXEC_PATH'] + \
+		'/scripts/python/Perf-Trace-Util/lib/Perf/Trace')
+
+from perf_trace_context import *
+from Core import *
+from Util import *
+
+drop_log = {}
+kallsyms = []
+
+def get_kallsyms_table():
+	global kallsyms
+	try:
+		f = open("/proc/kallsyms", "r")
+		linecount = 0
+		for line in f:
+			linecount = linecount+1
+		f.seek(0)
+	except:
+		return
+
+
+	j = 0
+	for line in f:
+		loc = int(line.split()[0], 16)
+		name = line.split()[2]
+		j = j +1
+		if ((j % 100) == 0):
+			print "\r" + str(j) + "/" + str(linecount),
+		kallsyms.append({ 'loc': loc, 'name' : name})
+
+	print "\r" + str(j) + "/" + str(linecount)
+	kallsyms.sort()
+	return
+
+def get_sym(sloc):
+	loc = int(sloc)
+	for i in kallsyms:
+		if (i['loc'] >= loc):
+			return (i['name'], i['loc']-loc)
+	return (None, 0)
+
+def print_drop_table():
+	print "%25s %25s %25s" % ("LOCATION", "OFFSET", "COUNT")
+	for i in drop_log.keys():
+		(sym, off) = get_sym(i)
+		if sym == None:
+			sym = i
+		print "%25s %25s %25s" % (sym, off, drop_log[i])
+
+
+def trace_begin():
+	print "Starting trace (Ctrl-C to dump results)"
+
+def trace_end():
+	print "Gathering kallsyms data"
+	get_kallsyms_table()
+	print_drop_table()
+
+# called from perf, when it finds a correspoinding event
+def skb__kfree_skb(name, context, cpu, sec, nsec, pid, comm,
+			skbaddr, protocol, location):
+	slocation = str(location)
+	try:
+		drop_log[slocation] = drop_log[slocation] + 1
+	except:
+		drop_log[slocation] = 1