[PATCH 14/17] tools/kvm_stat: add option '--guest'

[Stefan Raspl <raspl@linux.vnet.ibm.com>]

Add a new option '-g'/'--guest' to select a particular process by providing
the QEMU guest name.
Notes:
- The logic to figure out the pid corresponding to the guest name might look
  scary, but works pretty reliably in practice; in the unlikely event that it
  returns add'l flukes, it will bail out and hint at using '-p' instead, no
  harm done.
- Mixing '-g' and '-p' is possible, and the final instance specified on the
  command line is the significant one. This is consistent with current
  behavior for '-p' which, if specified multiple times, also regards the final
  instance as the significant one.

Signed-off-by: Stefan Raspl <raspl@linux.vnet.ibm.com>
---
 tools/kvm/kvm_stat/kvm_stat     | 101 +++++++++++++++++++++++++++++++++++++++-
 tools/kvm/kvm_stat/kvm_stat.txt |   6 +++
 2 files changed, 105 insertions(+), 2 deletions(-)

diff --git a/tools/kvm/kvm_stat/kvm_stat b/tools/kvm/kvm_stat/kvm_stat
index 17d2eff..ec77aac 100755
--- a/tools/kvm/kvm_stat/kvm_stat
+++ b/tools/kvm/kvm_stat/kvm_stat
@@ -30,6 +30,7 @@ import fcntl
 import resource
 import struct
 import re
+import subprocess
 from collections import defaultdict
 
 VMX_EXIT_REASONS = {
@@ -320,6 +321,30 @@ def parse_int_list(list_string):
     return integers
 
 
+def get_pid_from_gname(gname):
+    """Fuzzy function to convert guest name to QEMU process pid.
+
+    Returns a list of potential pids, can be empty if no match found.
+    Throws an exception on processing errors.
+
+    """
+    pids = []
+    try:
+        child = subprocess.Popen(['ps', '-A', '--format', 'pid,args'],
+                                 stdout=subprocess.PIPE)
+    except:
+        raise Exception
+    for line in child.stdout:
+        line = line.lstrip().split(' ', 1)
+        # perform a sanity check before calling the more expensive
+        # function to possibly extract the guest name
+        if ' -name ' in line[1] and gname == get_gname_from_pid(line[0]):
+            pids.append(int(line[0]))
+    child.stdout.close()
+
+    return pids
+
+
 def get_gname_from_pid(pid):
     """Returns the guest name for a QEMU process pid.
 
@@ -976,7 +1001,7 @@ class Tui(object):
             except re.error:
                 continue
 
-    def show_vm_selection(self):
+    def show_vm_selection_by_pid(self):
         """Draws PID selection mask.
 
         Asks for a pid until a valid pid or 0 has been entered.
@@ -1015,6 +1040,50 @@ class Tui(object):
                 msg = '"' + str(pid) + '": Not a valid pid'
                 continue
 
+    def show_vm_selection_by_guest_name(self):
+        """Draws guest selection mask.
+
+        Asks for a guest name until a valid guest name or '' is entered.
+
+        """
+        msg = ''
+        while True:
+            self.screen.erase()
+            self.screen.addstr(0, 0,
+                               'Show statistics for specific guest.',
+                               curses.A_BOLD)
+            self.screen.addstr(1, 0,
+                               'This might limit the shown data to the trace '
+                               'statistics.')
+            self.screen.addstr(5, 0, msg)
+            curses.echo()
+            self.screen.addstr(3, 0, "Guest [ENTER or guest]: ")
+            gname = self.screen.getstr()
+            curses.noecho()
+
+            if not gname:
+                self.refresh_header(0)
+                self.update_pid(0)
+                break
+            else:
+                pids = []
+                try:
+                    pids = get_pid_from_gname(gname)
+                except:
+                    msg = '"' + gname + '": Internal error while searching, ' \
+                          'use pid filter instead'
+                    continue
+                if len(pids) == 0:
+                    msg = '"' + gname + '": Not an active guest'
+                    continue
+                if len(pids) > 1:
+                    msg = '"' + gname + '": Multiple matches found, use pid ' \
+                          'filter instead'
+                    continue
+                self.refresh_header(pids[0])
+                self.update_pid(pids[0])
+                break
+
     def show_stats(self):
         """Refreshes the screen and processes user input."""
         sleeptime = DELAY_INITIAL
@@ -1034,8 +1103,11 @@ class Tui(object):
                 if char == 'f':
                     self.show_filter_selection()
                     sleeptime = DELAY_INITIAL
+                if char == 'g':
+                    self.show_vm_selection_by_guest_name()
+                    sleeptime = DELAY_INITIAL
                 if char == 'p':
-                    self.show_vm_selection()
+                    self.show_vm_selection_by_pid()
                     sleeptime = DELAY_INITIAL
             except KeyboardInterrupt:
                 break
@@ -1105,6 +1177,7 @@ Requirements:
 
 Interactive Commands:
    f     filter by regular expression
+   g     filter by guest name
    p     filter by PID
    q     quit
    x     toggle reporting of stats for individual child trace events
@@ -1118,6 +1191,22 @@ Press any other key to refresh statistics immediately.
             else:
                 return ""
 
+    def cb_guest_to_pid(option, opt, val, parser):
+        try:
+            pids = get_pid_from_gname(val)
+        except:
+            raise optparse.OptionValueError('Error while searching for guest '
+                                            '"{}", use "-p" to specify a pid '
+                                            'instead'.format(val))
+        if len(pids) == 0:
+            raise optparse.OptionValueError('No guest by the name "{}" '
+                                            'found'.format(val))
+        if len(pids) > 1:
+            raise optparse.OptionValueError('Multiple processes found (pids: '
+                                            '{}) - use "-p" to specify a pid '
+                                            'instead'.format(" ".join(pids)))
+        parser.values.pid = pids[0]
+
     optparser = optparse.OptionParser(description=description_text,
                                       formatter=PlainHelpFormatter())
     optparser.add_option('-1', '--once', '--batch',
@@ -1157,6 +1246,14 @@ Press any other key to refresh statistics immediately.
                          dest='pid',
                          help='restrict statistics to pid',
                          )
+    optparser.add_option('-g', '--guest',
+                         action='callback',
+                         type='string',
+                         dest='pid',
+                         metavar='GUEST',
+                         help='restrict statistics to guest by name',
+                         callback=cb_guest_to_pid,
+                         )
     (options, _) = optparser.parse_args(sys.argv)
     return options
 
diff --git a/tools/kvm/kvm_stat/kvm_stat.txt b/tools/kvm/kvm_stat/kvm_stat.txt
index 077bcc7..35587c3 100644
--- a/tools/kvm/kvm_stat/kvm_stat.txt
+++ b/tools/kvm/kvm_stat/kvm_stat.txt
@@ -31,6 +31,8 @@ INTERACTIVE COMMANDS
 [horizontal]
 *f*::	filter by regular expression
 
+*g*::	filter by guest name
+
 *p*::	filter by PID
 
 *q*::	quit
@@ -62,6 +64,10 @@ OPTIONS
 --pid=<pid>::
 	limit statistics to one virtual machine (pid)
 
+-g<guest>::
+--guest=<guest_name>::
+	limit statistics to one virtual machine (guest name)
+
 -f<fields>::
 --fields=<fields>::
 	fields to display (regex)
-- 
2.8.4