diff --git a/src/base/traceflags.py b/src/base/traceflags.py
index 800c24dee..dd5ade5af 100644
--- a/src/base/traceflags.py
+++ b/src/base/traceflags.py
@@ -29,19 +29,7 @@
 # Authors: Nathan Binkert
 #          Steve Reinhardt
 
-#
-# This file generates the header and source files for the flags
-# that control the tracing facility.
-#
-
-import sys
-
-if len(sys.argv) != 2:
-    print "%s: Need argument (basename of cc/hh files)" % sys.argv[0]
-    sys.exit(1)
-
-hhfilename = sys.argv[1] + '.hh'
-ccfilename = sys.argv[1] + '.cc'
+__all__ = [ 'allFlags', 'baseFlags', 'compoundFlagsMap', 'compoundFlags' ]
 
 #
 # The list of trace flags that can be used to condition DPRINTFs etc.
@@ -196,6 +184,13 @@ compoundFlagMap = {
     'ScsiAll'        : [ 'ScsiDisk', 'ScsiCtrl', 'ScsiNone' ]
 }
 
+# extract just the compound flag names into a list
+compoundFlags = []
+compoundFlags.extend(compoundFlagMap.keys())
+compoundFlags.sort()
+
+allFlags = frozenset(baseFlags + compoundFlags)
+
 #############################################################
 #
 # Everything below this point generates the appropriate C++
@@ -203,93 +198,84 @@ compoundFlagMap = {
 # adding or modifying flag definitions, you should not have to change
 # anything below.
 #
+def gen_hh(filename):
+    #
+    # First generate the header file.  This defines the Flag enum
+    # and some extern declarations for the .cc file.
+    #
+    try:
+        hhfile = file(filename, 'w')
+    except IOError, e:
+        sys.exit("can't open %s: %s" % (hhfilename, e))
 
-import sys
+    # file header boilerplate
+    print >>hhfile, '''
+    /*
+     * DO NOT EDIT THIS FILE!
+     *
+     * Automatically generated from traceflags.py
+     */
 
-# extract just the compound flag names into a list
-compoundFlags = []
-compoundFlags.extend(compoundFlagMap.keys())
-compoundFlags.sort()
+    #ifndef __BASE_TRACE_FLAGS_HH__
+    #define __BASE_TRACE_FLAGS_HH__
 
-#
-# First generate the header file.  This defines the Flag enum
-# and some extern declarations for the .cc file.
-#
-try:
-    hhfile = file(hhfilename, 'w')
-except IOError, e:
-    sys.exit("can't open %s: %s" % (hhfilename, e))
+    namespace Trace {
 
-# file header boilerplate
-print >>hhfile, '''
-/*
- * DO NOT EDIT THIS FILE!
- *
- * Automatically generated from traceflags.py
- */
+    enum Flags {
+    ''',
 
-#ifndef __BASE_TRACE_FLAGS_HH__
-#define __BASE_TRACE_FLAGS_HH__
+    # Generate the enum.  Base flags come first, then compound flags.
+    idx = 0
+    for flag in baseFlags:
+        print >>hhfile, '    %s = %d,' % (flag, idx)
+        idx += 1
 
-namespace Trace {
+    numBaseFlags = idx
+    print >>hhfile, '    NumFlags = %d,' % idx
 
-enum Flags {
-''',
+    # put a comment in here to separate base from compound flags
+    print >>hhfile, '''
+        // The remaining enum values are *not* valid indices for Trace::flags.
+        // They are "compound" flags, which correspond to sets of base
+        // flags, and are used only by TraceParamContext::setFlags().
+    ''',
 
-# Generate the enum.  Base flags come first, then compound flags.
-idx = 0
-for flag in baseFlags:
-    print >>hhfile, '    %s = %d,' % (flag, idx)
-    idx += 1
+    for flag in compoundFlags:
+        print >>hhfile, '    %s = %d,' % (flag, idx)
+        idx += 1
 
-numBaseFlags = idx
-print >>hhfile, '    NumFlags = %d,' % idx
+    numCompoundFlags = idx - numBaseFlags
+    print >>hhfile, '    NumCompoundFlags = %d' % numCompoundFlags
 
-# put a comment in here to separate base from compound flags
-print >>hhfile, '''
-    // The remaining enum values are *not* valid indices for Trace::flags.
-    // They are "compound" flags, which correspond to sets of base
-    // flags, and are used only by TraceParamContext::setFlags().
-''',
+    # trailer boilerplate
+    print >>hhfile, '''\
+    }; // enum Flags
 
-for flag in compoundFlags:
-    print >>hhfile, '    %s = %d,' % (flag, idx)
-    idx += 1
+    // Array of strings for SimpleEnumParam
+    extern const char *flagStrings[];
+    extern const int numFlagStrings;
 
-numCompoundFlags = idx - numBaseFlags
-print >>hhfile, '    NumCompoundFlags = %d' % numCompoundFlags
+    // Array of arraay pointers: for each compound flag, gives the list of
+    // base flags to set.  Inidividual flag arrays are terminated by -1.
+    extern const Flags *compoundFlags[];
 
-# trailer boilerplate
-print >>hhfile, '''\
-}; // enum Flags
+    /* namespace Trace */ }
 
-// Array of strings for SimpleEnumParam
-extern const char *flagStrings[];
-extern const int numFlagStrings;
+    #endif // __BASE_TRACE_FLAGS_HH__
+    ''',
 
-// Array of arraay pointers: for each compound flag, gives the list of
-// base flags to set.  Inidividual flag arrays are terminated by -1.
-extern const Flags *compoundFlags[];
+    hhfile.close()
 
-/* namespace Trace */ }
+def gen_cc(filename):
+    '''Print out .cc file with array definitions.'''
 
-#endif // __BASE_TRACE_FLAGS_HH__
-''',
+    try:
+        ccfile = file(filename, 'w')
+    except OSError, e:
+        sys.exit("can't open %s: %s" % (ccfilename, e))
 
-hhfile.close()
-
-#
-#
-# Print out .cc file with array definitions.
-#
-#
-try:
-    ccfile = file(ccfilename, 'w')
-except OSError, e:
-    sys.exit("can't open %s: %s" % (ccfilename, e))
-
-# file header
-print >>ccfile, '''
+    # file header
+    print >>ccfile, '''
 /*
  * DO NOT EDIT THIS FILE!
  *
@@ -304,45 +290,57 @@ const char *Trace::flagStrings[] =
 {
 ''',
 
-# The string array is used by SimpleEnumParam to map the strings
-# provided by the user to enum values.
-for flag in baseFlags:
-    print >>ccfile, '    "%s",' % flag
+    # The string array is used by SimpleEnumParam to map the strings
+    # provided by the user to enum values.
+    for flag in baseFlags:
+        print >>ccfile, '    "%s",' % flag
 
-for flag in compoundFlags:
-    print >>ccfile, '    "%s",' % flag
+    for flag in compoundFlags:
+        print >>ccfile, '    "%s",' % flag
 
-print >>ccfile, '};\n'
+    print >>ccfile, '};\n'
 
-numFlagStrings = len(baseFlags) + len(compoundFlags);
+    numFlagStrings = len(baseFlags) + len(compoundFlags);
 
-print >>ccfile, 'const int Trace::numFlagStrings = %d;' % numFlagStrings
-print >>ccfile
-
-#
-# Now define the individual compound flag arrays.  There is an array
-# for each compound flag listing the component base flags.
-#
-
-for flag in compoundFlags:
-    flags = compoundFlagMap[flag]
-    flags.append('(Flags)-1')
-    print >>ccfile, 'static const Flags %sMap[] =' % flag
-    print >>ccfile, '{ %s };' % (', '.join(flags))
+    print >>ccfile, 'const int Trace::numFlagStrings = %d;' % numFlagStrings
     print >>ccfile
 
-#
-# Finally the compoundFlags[] array maps the compound flags
-# to their individual arrays/
-#
-print >>ccfile, 'const Flags *Trace::compoundFlags[] ='
-print >>ccfile, '{'
+    #
+    # Now define the individual compound flag arrays.  There is an array
+    # for each compound flag listing the component base flags.
+    #
 
-for flag in compoundFlags:
-    print >>ccfile, '    %sMap,' % flag
+    for flag in compoundFlags:
+        flags = compoundFlagMap[flag]
+        flags.append('(Flags)-1')
+        print >>ccfile, 'static const Flags %sMap[] =' % flag
+        print >>ccfile, '{ %s };' % (', '.join(flags))
+        print >>ccfile
 
-# file trailer
-print >>ccfile, '};'
+    #
+    # Finally the compoundFlags[] array maps the compound flags
+    # to their individual arrays/
+    #
+    print >>ccfile, 'const Flags *Trace::compoundFlags[] ='
+    print >>ccfile, '{'
 
-ccfile.close()
+    for flag in compoundFlags:
+        print >>ccfile, '    %sMap,' % flag
 
+    # file trailer
+    print >>ccfile, '};'
+
+    ccfile.close()
+
+if __name__ == '__main__':
+    # This file generates the header and source files for the flags
+    # that control the tracing facility.
+
+    import sys
+
+    if len(sys.argv) != 2:
+        print "%s: Need argument (basename of cc/hh files)" % sys.argv[0]
+        sys.exit(1)
+
+    gen_hh(sys.argv[1] + '.hh')
+    gen_cc(sys.argv[1] + '.cc')
diff --git a/src/python/SConscript b/src/python/SConscript
index 61cab45f3..51271650f 100644
--- a/src/python/SConscript
+++ b/src/python/SConscript
@@ -97,6 +97,7 @@ addPkg('m5')
 pyzip_files.append('m5/defines.py')
 pyzip_files.append('m5/info.py')
 pyzip_files.append(join(env['ROOT'], 'util/pbs/jobfile.py'))
+pyzip_files.append(join(env['ROOT'], 'src/base/traceflags.py'))
 
 def swig_it(basename):
     env.Command(['swig/%s_wrap.cc' % basename, 'm5/internal/%s.py' % basename],
diff --git a/src/python/m5/main.py b/src/python/m5/main.py
index d02bc466b..d42137264 100644
--- a/src/python/m5/main.py
+++ b/src/python/m5/main.py
@@ -29,6 +29,7 @@
 import code, optparse, os, socket, sys
 from datetime import datetime
 from attrdict import attrdict
+import traceflags
 
 __all__ = [ 'options', 'arguments', 'main' ]
 
@@ -40,6 +41,19 @@ The Regents of The University of Michigan
 All Rights Reserved
 '''
 
+def print_list(items, indent=4):
+    line = ' ' * indent
+    for i,item in enumerate(items):
+        if len(line) + len(item) > 76:
+            print line
+            line = ' ' * indent
+
+        if i < len(items) - 1:
+            line += '%s, ' % item
+        else:
+            line += item
+            print line
+
 # there's only one option parsing done, so make it global and add some
 # helper functions to make it work well.
 parser = optparse.OptionParser(usage=usage, version=version,
@@ -135,8 +149,10 @@ add_option("--debug-break", metavar="TIME[,TIME]", action='append', split=',',
 
 # Tracing options
 set_group("Trace Options")
+add_option("--trace-help", action='store_true',
+    help="Print help on trace flags")
 add_option("--trace-flags", metavar="FLAG[,FLAG]", action='append', split=',',
-    help="Sets the flags for tracing")
+    help="Sets the flags for tracing (-FLAG disables a flag)")
 add_option("--trace-start", metavar="TIME", type='int',
     help="Start tracing at TIME (must be in ticks)")
 add_option("--trace-file", metavar="FILE", default="cout",
@@ -231,6 +247,19 @@ def main():
         print info.RELEASE_NOTES
         print
 
+    if options.trace_help:
+        done = True
+        print "Base Flags:"
+        print_list(traceflags.baseFlags, indent=4)
+        print
+        print "Compound Flags:"
+        for flag in traceflags.compoundFlags:
+            if flag == 'All':
+                continue
+            print "    %s:" % flag
+            print_list(traceflags.compoundFlagMap[flag], indent=8)
+            print
+
     if done:
         sys.exit(0)
 
@@ -250,6 +279,7 @@ def main():
     if not arguments or not os.path.isfile(arguments[0]):
         if arguments and not os.path.isfile(arguments[0]):
             print "Script %s not found" % arguments[0]
+
         usage(2)
 
     # tell C++ about output directory
@@ -267,9 +297,28 @@ def main():
     for when in options.debug_break:
         internal.debug.schedBreakCycle(int(when))
 
+    on_flags = []
+    off_flags = []
     for flag in options.trace_flags:
+        off = False
+        if flag.startswith('-'):
+            flag = flag[1:]
+            off = True
+        if flag not in traceflags.allFlags:
+            print >>sys.stderr, "invalid trace flag '%s'" % flag
+            sys.exit(1)
+
+        if off:
+            off_flags.append(flag)
+        else:
+            on_flags.append(flag)
+
+    for flag in on_flags:
         internal.trace.set(flag)
 
+    for flag in off_flags:
+        internal.trace.clear(flag)
+
     if options.trace_start is not None:
         internal.trace.enabled = False
         def enable_trace():