tools: Add kvm_stat vm monitor script

This tool displays kvm vm exit statistics to ease vm monitoring. It
takes its data from the kvm debugfs files or the vm tracepoints and
outputs them as a curses ui or simple text.

It was moved from qemu, as it is dependent on the kernel whereas qemu
works with a large number of kernel versions, some of which may break
the script.

Signed-off-by: Janosch Frank <frankja@linux.vnet.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

2 files changed, 830 insertions, 0 deletions

diff --git a/tools/kvm/kvm_stat/Makefile b/tools/kvm/kvm_stat/Makefile
new file mode 100644
index 0000000..c639b8d
--- /dev/null
+++ b/tools/kvm/kvm_stat/Makefile
@@ -0,0 +1,5 @@
+BINDIR=usr/bin
+
+install:
+	mkdir -p $(INSTALL_ROOT)/$(BINDIR)
+	install -m 755 -p "kvm_stat" "$(INSTALL_ROOT)/$(BINDIR)/$(TARGET)"
diff --git a/tools/kvm/kvm_stat/kvm_stat b/tools/kvm/kvm_stat/kvm_stat
new file mode 100755
index 0000000..769d884
--- /dev/null
+++ b/tools/kvm/kvm_stat/kvm_stat
@@ -0,0 +1,825 @@
+#!/usr/bin/python
+#
+# top-like utility for displaying kvm statistics
+#
+# Copyright 2006-2008 Qumranet Technologies
+# Copyright 2008-2011 Red Hat, Inc.
+#
+# Authors:
+#  Avi Kivity <avi@redhat.com>
+#
+# This work is licensed under the terms of the GNU GPL, version 2.  See
+# the COPYING file in the top-level directory.
+
+import curses
+import sys
+import os
+import time
+import optparse
+import ctypes
+import fcntl
+import resource
+import struct
+import re
+from collections import defaultdict
+from time import sleep
+
+VMX_EXIT_REASONS = {
+    'EXCEPTION_NMI':        0,
+    'EXTERNAL_INTERRUPT':   1,
+    'TRIPLE_FAULT':         2,
+    'PENDING_INTERRUPT':    7,
+    'NMI_WINDOW':           8,
+    'TASK_SWITCH':          9,
+    'CPUID':                10,
+    'HLT':                  12,
+    'INVLPG':               14,
+    'RDPMC':                15,
+    'RDTSC':                16,
+    'VMCALL':               18,
+    'VMCLEAR':              19,
+    'VMLAUNCH':             20,
+    'VMPTRLD':              21,
+    'VMPTRST':              22,
+    'VMREAD':               23,
+    'VMRESUME':             24,
+    'VMWRITE':              25,
+    'VMOFF':                26,
+    'VMON':                 27,
+    'CR_ACCESS':            28,
+    'DR_ACCESS':            29,
+    'IO_INSTRUCTION':       30,
+    'MSR_READ':             31,
+    'MSR_WRITE':            32,
+    'INVALID_STATE':        33,
+    'MWAIT_INSTRUCTION':    36,
+    'MONITOR_INSTRUCTION':  39,
+    'PAUSE_INSTRUCTION':    40,
+    'MCE_DURING_VMENTRY':   41,
+    'TPR_BELOW_THRESHOLD':  43,
+    'APIC_ACCESS':          44,
+    'EPT_VIOLATION':        48,
+    'EPT_MISCONFIG':        49,
+    'WBINVD':               54,
+    'XSETBV':               55,
+    'APIC_WRITE':           56,
+    'INVPCID':              58,
+}
+
+SVM_EXIT_REASONS = {
+    'READ_CR0':       0x000,
+    'READ_CR3':       0x003,
+    'READ_CR4':       0x004,
+    'READ_CR8':       0x008,
+    'WRITE_CR0':      0x010,
+    'WRITE_CR3':      0x013,
+    'WRITE_CR4':      0x014,
+    'WRITE_CR8':      0x018,
+    'READ_DR0':       0x020,
+    'READ_DR1':       0x021,
+    'READ_DR2':       0x022,
+    'READ_DR3':       0x023,
+    'READ_DR4':       0x024,
+    'READ_DR5':       0x025,
+    'READ_DR6':       0x026,
+    'READ_DR7':       0x027,
+    'WRITE_DR0':      0x030,
+    'WRITE_DR1':      0x031,
+    'WRITE_DR2':      0x032,
+    'WRITE_DR3':      0x033,
+    'WRITE_DR4':      0x034,
+    'WRITE_DR5':      0x035,
+    'WRITE_DR6':      0x036,
+    'WRITE_DR7':      0x037,
+    'EXCP_BASE':      0x040,
+    'INTR':           0x060,
+    'NMI':            0x061,
+    'SMI':            0x062,
+    'INIT':           0x063,
+    'VINTR':          0x064,
+    'CR0_SEL_WRITE':  0x065,
+    'IDTR_READ':      0x066,
+    'GDTR_READ':      0x067,
+    'LDTR_READ':      0x068,
+    'TR_READ':        0x069,
+    'IDTR_WRITE':     0x06a,
+    'GDTR_WRITE':     0x06b,
+    'LDTR_WRITE':     0x06c,
+    'TR_WRITE':       0x06d,
+    'RDTSC':          0x06e,
+    'RDPMC':          0x06f,
+    'PUSHF':          0x070,
+    'POPF':           0x071,
+    'CPUID':          0x072,
+    'RSM':            0x073,
+    'IRET':           0x074,
+    'SWINT':          0x075,
+    'INVD':           0x076,
+    'PAUSE':          0x077,
+    'HLT':            0x078,
+    'INVLPG':         0x079,
+    'INVLPGA':        0x07a,
+    'IOIO':           0x07b,
+    'MSR':            0x07c,
+    'TASK_SWITCH':    0x07d,
+    'FERR_FREEZE':    0x07e,
+    'SHUTDOWN':       0x07f,
+    'VMRUN':          0x080,
+    'VMMCALL':        0x081,
+    'VMLOAD':         0x082,
+    'VMSAVE':         0x083,
+    'STGI':           0x084,
+    'CLGI':           0x085,
+    'SKINIT':         0x086,
+    'RDTSCP':         0x087,
+    'ICEBP':          0x088,
+    'WBINVD':         0x089,
+    'MONITOR':        0x08a,
+    'MWAIT':          0x08b,
+    'MWAIT_COND':     0x08c,
+    'XSETBV':         0x08d,
+    'NPF':            0x400,
+}
+
+# EC definition of HSR (from arch/arm64/include/asm/kvm_arm.h)
+AARCH64_EXIT_REASONS = {
+    'UNKNOWN':      0x00,
+    'WFI':          0x01,
+    'CP15_32':      0x03,
+    'CP15_64':      0x04,
+    'CP14_MR':      0x05,
+    'CP14_LS':      0x06,
+    'FP_ASIMD':     0x07,
+    'CP10_ID':      0x08,
+    'CP14_64':      0x0C,
+    'ILL_ISS':      0x0E,
+    'SVC32':        0x11,
+    'HVC32':        0x12,
+    'SMC32':        0x13,
+    'SVC64':        0x15,
+    'HVC64':        0x16,
+    'SMC64':        0x17,
+    'SYS64':        0x18,
+    'IABT':         0x20,
+    'IABT_HYP':     0x21,
+    'PC_ALIGN':     0x22,
+    'DABT':         0x24,
+    'DABT_HYP':     0x25,
+    'SP_ALIGN':     0x26,
+    'FP_EXC32':     0x28,
+    'FP_EXC64':     0x2C,
+    'SERROR':       0x2F,
+    'BREAKPT':      0x30,
+    'BREAKPT_HYP':  0x31,
+    'SOFTSTP':      0x32,
+    'SOFTSTP_HYP':  0x33,
+    'WATCHPT':      0x34,
+    'WATCHPT_HYP':  0x35,
+    'BKPT32':       0x38,
+    'VECTOR32':     0x3A,
+    'BRK64':        0x3C,
+}
+
+# From include/uapi/linux/kvm.h, KVM_EXIT_xxx
+USERSPACE_EXIT_REASONS = {
+    'UNKNOWN':          0,
+    'EXCEPTION':        1,
+    'IO':               2,
+    'HYPERCALL':        3,
+    'DEBUG':            4,
+    'HLT':              5,
+    'MMIO':             6,
+    'IRQ_WINDOW_OPEN':  7,
+    'SHUTDOWN':         8,
+    'FAIL_ENTRY':       9,
+    'INTR':             10,
+    'SET_TPR':          11,
+    'TPR_ACCESS':       12,
+    'S390_SIEIC':       13,
+    'S390_RESET':       14,
+    'DCR':              15,
+    'NMI':              16,
+    'INTERNAL_ERROR':   17,
+    'OSI':              18,
+    'PAPR_HCALL':       19,
+    'S390_UCONTROL':    20,
+    'WATCHDOG':         21,
+    'S390_TSCH':        22,
+    'EPR':              23,
+    'SYSTEM_EVENT':     24,
+}
+
+IOCTL_NUMBERS = {
+    'SET_FILTER':  0x40082406,
+    'ENABLE':      0x00002400,
+    'DISABLE':     0x00002401,
+    'RESET':       0x00002403,
+}
+
+class Arch(object):
+    """Class that encapsulates global architecture specific data like
+    syscall and ioctl numbers.
+
+    """
+    @staticmethod
+    def get_arch():
+        machine = os.uname()[4]
+
+        if machine.startswith('ppc'):
+            return ArchPPC()
+        elif machine.startswith('aarch64'):
+            return ArchA64()
+        elif machine.startswith('s390'):
+            return ArchS390()
+        else:
+            # X86_64
+            for line in open('/proc/cpuinfo'):
+                if not line.startswith('flags'):
+                    continue
+
+                flags = line.split()
+                if 'vmx' in flags:
+                    return ArchX86(VMX_EXIT_REASONS)
+                if 'svm' in flags:
+                    return ArchX86(SVM_EXIT_REASONS)
+                return
+
+class ArchX86(Arch):
+    def __init__(self, exit_reasons):
+        self.sc_perf_evt_open = 298
+        self.ioctl_numbers = IOCTL_NUMBERS
+        self.exit_reasons = exit_reasons
+
+class ArchPPC(Arch):
+    def __init__(self):
+        self.sc_perf_evt_open = 319
+        self.ioctl_numbers = IOCTL_NUMBERS
+        self.ioctl_numbers['ENABLE'] = 0x20002400
+        self.ioctl_numbers['DISABLE'] = 0x20002401
+
+        # PPC comes in 32 and 64 bit and some generated ioctl
+        # numbers depend on the wordsize.
+        char_ptr_size = ctypes.sizeof(ctypes.c_char_p)
+        self.ioctl_numbers['SET_FILTER'] = 0x80002406 | char_ptr_size << 16
+
+class ArchA64(Arch):
+    def __init__(self):
+        self.sc_perf_evt_open = 241
+        self.ioctl_numbers = IOCTL_NUMBERS
+        self.exit_reasons = AARCH64_EXIT_REASONS
+
+class ArchS390(Arch):
+    def __init__(self):
+        self.sc_perf_evt_open = 331
+        self.ioctl_numbers = IOCTL_NUMBERS
+        self.exit_reasons = None
+
+ARCH = Arch.get_arch()
+
+
+def walkdir(path):
+    """Returns os.walk() data for specified directory.
+
+    As it is only a wrapper it returns the same 3-tuple of (dirpath,
+    dirnames, filenames).
+    """
+    return next(os.walk(path))
+
+
+def parse_int_list(list_string):
+    """Returns an int list from a string of comma separated integers and
+    integer ranges."""
+    integers = []
+    members = list_string.split(',')
+
+    for member in members:
+        if '-' not in member:
+            integers.append(int(member))
+        else:
+            int_range = member.split('-')
+            integers.extend(range(int(int_range[0]),
+                                  int(int_range[1]) + 1))
+
+    return integers
+
+
+def get_online_cpus():
+    with open('/sys/devices/system/cpu/online') as cpu_list:
+        cpu_string = cpu_list.readline()
+        return parse_int_list(cpu_string)
+
+
+def get_filters():
+    filters = {}
+    filters['kvm_userspace_exit'] = ('reason', USERSPACE_EXIT_REASONS)
+    if ARCH.exit_reasons:
+        filters['kvm_exit'] = ('exit_reason', ARCH.exit_reasons)
+    return filters
+
+libc = ctypes.CDLL('libc.so.6', use_errno=True)
+syscall = libc.syscall
+
+class perf_event_attr(ctypes.Structure):
+    _fields_ = [('type', ctypes.c_uint32),
+                ('size', ctypes.c_uint32),
+                ('config', ctypes.c_uint64),
+                ('sample_freq', ctypes.c_uint64),
+                ('sample_type', ctypes.c_uint64),
+                ('read_format', ctypes.c_uint64),
+                ('flags', ctypes.c_uint64),
+                ('wakeup_events', ctypes.c_uint32),
+                ('bp_type', ctypes.c_uint32),
+                ('bp_addr', ctypes.c_uint64),
+                ('bp_len', ctypes.c_uint64),
+                ]
+
+    def __init__(self):
+        super(self.__class__, self).__init__()
+        self.type = PERF_TYPE_TRACEPOINT
+        self.size = ctypes.sizeof(self)
+        self.read_format = PERF_FORMAT_GROUP
+
+def perf_event_open(attr, pid, cpu, group_fd, flags):
+    return syscall(ARCH.sc_perf_evt_open, ctypes.pointer(attr),
+                   ctypes.c_int(pid), ctypes.c_int(cpu),
+                   ctypes.c_int(group_fd), ctypes.c_long(flags))
+
+PERF_TYPE_TRACEPOINT = 2
+PERF_FORMAT_GROUP = 1 << 3
+
+PATH_DEBUGFS_TRACING = '/sys/kernel/debug/tracing'
+PATH_DEBUGFS_KVM = '/sys/kernel/debug/kvm'
+
+class Group(object):
+    def __init__(self):
+        self.events = []
+
+    def add_event(self, event):
+        self.events.append(event)
+
+    def read(self):
+        length = 8 * (1 + len(self.events))
+        read_format = 'xxxxxxxx' + 'Q' * len(self.events)
+        return dict(zip([event.name for event in self.events],
+                        struct.unpack(read_format,
+                                      os.read(self.events[0].fd, length))))
+
+class Event(object):
+    def __init__(self, name, group, trace_cpu, trace_point, trace_filter,
+                 trace_set='kvm'):
+        self.name = name
+        self.fd = None
+        self.setup_event(group, trace_cpu, trace_point, trace_filter,
+                         trace_set)
+
+    def setup_event_attribute(self, trace_set, trace_point):
+        id_path = os.path.join(PATH_DEBUGFS_TRACING, 'events', trace_set,
+                               trace_point, 'id')
+
+        event_attr = perf_event_attr()
+        event_attr.config = int(open(id_path).read())
+        return event_attr
+
+    def setup_event(self, group, trace_cpu, trace_point, trace_filter,
+                    trace_set):
+        event_attr = self.setup_event_attribute(trace_set, trace_point)
+
+        group_leader = -1
+        if group.events:
+            group_leader = group.events[0].fd
+
+        fd = perf_event_open(event_attr, -1, trace_cpu,
+                             group_leader, 0)
+        if fd == -1:
+            err = ctypes.get_errno()
+            raise OSError(err, os.strerror(err),
+                          'while calling sys_perf_event_open().')
+
+        if trace_filter:
+            fcntl.ioctl(fd, ARCH.ioctl_numbers['SET_FILTER'],
+                        trace_filter)
+
+        self.fd = fd
+
+    def enable(self):
+        fcntl.ioctl(self.fd, ARCH.ioctl_numbers['ENABLE'], 0)
+
+    def disable(self):
+        fcntl.ioctl(self.fd, ARCH.ioctl_numbers['DISABLE'], 0)
+
+    def reset(self):
+        fcntl.ioctl(self.fd, ARCH.ioctl_numbers['RESET'], 0)
+
+class TracepointProvider(object):
+    def __init__(self):
+        self.group_leaders = []
+        self.filters = get_filters()
+        self._fields = self.get_available_fields()
+        self.setup_traces()
+        self.fields = self._fields
+
+    def get_available_fields(self):
+        path = os.path.join(PATH_DEBUGFS_TRACING, 'events', 'kvm')
+        fields = walkdir(path)[1]
+        extra = []
+        for field in fields:
+            if field in self.filters:
+                filter_name_, filter_dicts = self.filters[field]
+                for name in filter_dicts:
+                    extra.append(field + '(' + name + ')')
+        fields += extra
+        return fields
+
+    def setup_traces(self):
+        cpus = get_online_cpus()
+
+        # The constant is needed as a buffer for python libs, std
+        # streams and other files that the script opens.
+        newlim = len(cpus) * len(self._fields) + 50
+        try:
+            softlim_, hardlim = resource.getrlimit(resource.RLIMIT_NOFILE)
+
+            if hardlim < newlim:
+                # Now we need CAP_SYS_RESOURCE, to increase the hard limit.
+                resource.setrlimit(resource.RLIMIT_NOFILE, (newlim, newlim))
+            else:
+                # Raising the soft limit is sufficient.
+                resource.setrlimit(resource.RLIMIT_NOFILE, (newlim, hardlim))
+
+        except ValueError:
+            sys.exit("NOFILE rlimit could not be raised to {0}".format(newlim))
+
+        for cpu in cpus:
+            group = Group()
+            for name in self._fields:
+                tracepoint = name
+                tracefilter = None
+                match = re.match(r'(.*)\((.*)\)', name)
+                if match:
+                    tracepoint, sub = match.groups()
+                    tracefilter = ('%s==%d\0' %
+                                   (self.filters[tracepoint][0],
+                                    self.filters[tracepoint][1][sub]))
+
+                group.add_event(Event(name=name,
+                                      group=group,
+                                      trace_cpu=cpu,
+                                      trace_point=tracepoint,
+                                      trace_filter=tracefilter))
+            self.group_leaders.append(group)
+
+    def available_fields(self):
+        return self.get_available_fields()
+
+    @property
+    def fields(self):
+        return self._fields
+
+    @fields.setter
+    def fields(self, fields):
+        self._fields = fields
+        for group in self.group_leaders:
+            for index, event in enumerate(group.events):
+                if event.name in fields:
+                    event.reset()
+                    event.enable()
+                else:
+                    # Do not disable the group leader.
+                    # It would disable all of its events.
+                    if index != 0:
+                        event.disable()
+
+    def read(self):
+        ret = defaultdict(int)
+        for group in self.group_leaders:
+            for name, val in group.read().iteritems():
+                if name in self._fields:
+                    ret[name] += val
+        return ret
+
+class DebugfsProvider(object):
+    def __init__(self):
+        self._fields = self.get_available_fields()
+
+    def get_available_fields(self):
+        return walkdir(PATH_DEBUGFS_KVM)[2]
+
+    @property
+    def fields(self):
+        return self._fields
+
+    @fields.setter
+    def fields(self, fields):
+        self._fields = fields
+
+    def read(self):
+        def val(key):
+            return int(file(PATH_DEBUGFS_KVM + '/' + key).read())
+        return dict([(key, val(key)) for key in self._fields])
+
+class Stats(object):
+    def __init__(self, providers, fields=None):
+        self.providers = providers
+        self._fields_filter = fields
+        self.values = {}
+        self.update_provider_filters()
+
+    def update_provider_filters(self):
+        def wanted(key):
+            if not self._fields_filter:
+                return True
+            return re.match(self._fields_filter, key) is not None
+
+        # As we reset the counters when updating the fields we can
+        # also clear the cache of old values.
+        self.values = {}
+        for provider in self.providers:
+            provider_fields = [key for key in provider.get_available_fields()
+                               if wanted(key)]
+            provider.fields = provider_fields
+
+    @property
+    def fields_filter(self):
+        return self._fields_filter
+
+    @fields_filter.setter
+    def fields_filter(self, fields_filter):
+        self._fields_filter = fields_filter
+        self.update_provider_filters()
+
+    def get(self):
+        for provider in self.providers:
+            new = provider.read()
+            for key in provider.fields:
+                oldval = self.values.get(key, (0, 0))
+                newval = new.get(key, 0)
+                newdelta = None
+                if oldval is not None:
+                    newdelta = newval - oldval[0]
+                self.values[key] = (newval, newdelta)
+        return self.values
+
+LABEL_WIDTH = 40
+NUMBER_WIDTH = 10
+
+class Tui(object):
+    def __init__(self, stats):
+        self.stats = stats
+        self.screen = None
+        self.drilldown = False
+        self.update_drilldown()
+
+    def __enter__(self):
+        """Initialises curses for later use.  Based on curses.wrapper
+           implementation from the Python standard library."""
+        self.screen = curses.initscr()
+        curses.noecho()
+        curses.cbreak()
+
+        # The try/catch works around a minor bit of
+        # over-conscientiousness in the curses module, the error
+        # return from C start_color() is ignorable.
+        try:
+            curses.start_color()
+        except:
+            pass
+
+        curses.use_default_colors()
+        return self
+
+    def __exit__(self, *exception):
+        """Resets the terminal to its normal state.  Based on curses.wrappre
+           implementation from the Python standard library."""
+        if self.screen:
+            self.screen.keypad(0)
+            curses.echo()
+            curses.nocbreak()
+            curses.endwin()
+
+    def update_drilldown(self):
+        if not self.stats.fields_filter:
+            self.stats.fields_filter = r'^[^\(]*$'
+
+        elif self.stats.fields_filter == r'^[^\(]*$':
+            self.stats.fields_filter = None
+
+    def refresh(self, sleeptime):
+        self.screen.erase()
+        self.screen.addstr(0, 0, 'kvm statistics - summary', curses.A_BOLD)
+        self.screen.addstr(2, 1, 'Event')
+        self.screen.addstr(2, 1 + LABEL_WIDTH + NUMBER_WIDTH -
+                           len('Total'), 'Total')
+        self.screen.addstr(2, 1 + LABEL_WIDTH + NUMBER_WIDTH + 8 -
+                           len('Current'), 'Current')
+        row = 3
+        stats = self.stats.get()
+        def sortkey(x):
+            if stats[x][1]:
+                return (-stats[x][1], -stats[x][0])
+            else:
+                return (0, -stats[x][0])
+        for key in sorted(stats.keys(), key=sortkey):
+
+            if row >= self.screen.getmaxyx()[0]:
+                break
+            values = stats[key]
+            if not values[0] and not values[1]:
+                break
+            col = 1
+            self.screen.addstr(row, col, key)
+            col += LABEL_WIDTH
+            self.screen.addstr(row, col, '%10d' % (values[0],))
+            col += NUMBER_WIDTH
+            if values[1] is not None:
+                self.screen.addstr(row, col, '%8d' % (values[1] / sleeptime,))
+            row += 1
+        self.screen.refresh()
+
+    def show_filter_selection(self):
+        while True:
+            self.screen.erase()
+            self.screen.addstr(0, 0,
+                               "Show statistics for events matching a regex.",
+                               curses.A_BOLD)
+            self.screen.addstr(2, 0,
+                               "Current regex: {0}"
+                               .format(self.stats.fields_filter))
+            self.screen.addstr(3, 0, "New regex: ")
+            curses.echo()
+            regex = self.screen.getstr()
+            curses.noecho()
+            if len(regex) == 0:
+                return
+            try:
+                re.compile(regex)
+                self.stats.fields_filter = regex
+                return
+            except re.error:
+                continue
+
+    def show_stats(self):
+        sleeptime = 0.25
+        while True:
+            self.refresh(sleeptime)
+            curses.halfdelay(int(sleeptime * 10))
+            sleeptime = 3
+            try:
+                char = self.screen.getkey()
+                if char == 'x':
+                    self.drilldown = not self.drilldown
+                    self.update_drilldown()
+                if char == 'q':
+                    break
+                if char == 'f':
+                    self.show_filter_selection()
+            except KeyboardInterrupt:
+                break
+            except curses.error:
+                continue
+
+def batch(stats):
+    s = stats.get()
+    time.sleep(1)
+    s = stats.get()
+    for key in sorted(s.keys()):
+        values = s[key]
+        print '%-42s%10d%10d' % (key, values[0], values[1])
+
+def log(stats):
+    keys = sorted(stats.get().iterkeys())
+    def banner():
+        for k in keys:
+            print '%s' % k,
+        print
+    def statline():
+        s = stats.get()
+        for k in keys:
+            print ' %9d' % s[k][1],
+        print
+    line = 0
+    banner_repeat = 20
+    while True:
+        time.sleep(1)
+        if line % banner_repeat == 0:
+            banner()
+        statline()
+        line += 1
+
+def get_options():
+    description_text = """
+This script displays various statistics about VMs running under KVM.
+The statistics are gathered from the KVM debugfs entries and / or the
+currently available perf traces.
+
+The monitoring takes additional cpu cycles and might affect the VM's
+performance.
+
+Requirements:
+- Access to:
+    /sys/kernel/debug/kvm
+    /sys/kernel/debug/trace/events/*
+    /proc/pid/task
+- /proc/sys/kernel/perf_event_paranoid < 1 if user has no
+  CAP_SYS_ADMIN and perf events are used.
+- CAP_SYS_RESOURCE if the hard limit is not high enough to allow
+  the large number of files that are possibly opened.
+"""
+
+    class PlainHelpFormatter(optparse.IndentedHelpFormatter):
+        def format_description(self, description):
+            if description:
+                return description + "\n"
+            else:
+                return ""
+
+    optparser = optparse.OptionParser(description=description_text,
+                                      formatter=PlainHelpFormatter())
+    optparser.add_option('-1', '--once', '--batch',
+                         action='store_true',
+                         default=False,
+                         dest='once',
+                         help='run in batch mode for one second',
+                         )
+    optparser.add_option('-l', '--log',
+                         action='store_true',
+                         default=False,
+                         dest='log',
+                         help='run in logging mode (like vmstat)',
+                         )
+    optparser.add_option('-t', '--tracepoints',
+                         action='store_true',
+                         default=False,
+                         dest='tracepoints',
+                         help='retrieve statistics from tracepoints',
+                         )
+    optparser.add_option('-d', '--debugfs',
+                         action='store_true',
+                         default=False,
+                         dest='debugfs',
+                         help='retrieve statistics from debugfs',
+                         )
+    optparser.add_option('-f', '--fields',
+                         action='store',
+                         default=None,
+                         dest='fields',
+                         help='fields to display (regex)',
+                         )
+    (options, _) = optparser.parse_args(sys.argv)
+    return options
+
+def get_providers(options):
+    providers = []
+
+    if options.tracepoints:
+        providers.append(TracepointProvider())
+    if options.debugfs:
+        providers.append(DebugfsProvider())
+    if len(providers) == 0:
+        providers.append(TracepointProvider())
+
+    return providers
+
+def check_access(options):
+    if not os.path.exists('/sys/kernel/debug'):
+        sys.stderr.write('Please enable CONFIG_DEBUG_FS in your kernel.')
+        sys.exit(1)
+
+    if not os.path.exists(PATH_DEBUGFS_KVM):
+        sys.stderr.write("Please make sure, that debugfs is mounted and "
+                         "readable by the current user:\n"
+                         "('mount -t debugfs debugfs /sys/kernel/debug')\n"
+                         "Also ensure, that the kvm modules are loaded.\n")
+        sys.exit(1)
+
+    if not os.path.exists(PATH_DEBUGFS_TRACING) and (options.tracepoints
+                                                     or not options.debugfs):
+        sys.stderr.write("Please enable CONFIG_TRACING in your kernel "
+                         "when using the option -t (default).\n"
+                         "If it is enabled, make {0} readable by the "
+                         "current user.\n"
+                         .format(PATH_DEBUGFS_TRACING))
+        if options.tracepoints:
+            sys.exit(1)
+
+        sys.stderr.write("Falling back to debugfs statistics!\n")
+        options.debugfs = True
+        sleep(5)
+
+    return options
+
+def main():
+    options = get_options()
+    options = check_access(options)
+    providers = get_providers(options)
+    stats = Stats(providers, fields=options.fields)
+
+    if options.log:
+        log(stats)
+    elif not options.once:
+        with Tui(stats) as tui:
+            tui.show_stats()
+    else:
+        batch(stats)
+
+if __name__ == "__main__":
+    main()