[PATCH 0/3] tools/kvm_stat: add logfile support

[PATCH 0/3] tools/kvm_stat: add logfile support

[Stefan Raspl]

Next attempt to come up with support for logfiles that can be combined
with a solution for rotating logs.
Adding another patch to skip records with all zeros to preserve space.

Stefan Raspl (3):
  tools/kvm_stat: add command line switch '-z' to skip zero records
  tools/kvm_stat: Add command line switch '-L' to log to file
  tools/kvm_stat: add sample systemd unit file

 tools/kvm/kvm_stat/kvm_stat         | 110 ++++++++++++++++++++++++----
 tools/kvm/kvm_stat/kvm_stat.service |  16 ++++
 tools/kvm/kvm_stat/kvm_stat.txt     |   9 +++
 3 files changed, 121 insertions(+), 14 deletions(-)
 create mode 100644 tools/kvm/kvm_stat/kvm_stat.service

-- 
2.17.1

[PATCH 1/3] tools/kvm_stat: add command line switch '-z' to skip zero records

[Stefan Raspl]

From: Stefan Raspl <raspl@de.ibm.com>

When running in logging mode, skip records with all zeros (=empty records)
to preserve space when logging to files.

Signed-off-by: Stefan Raspl <raspl@linux.ibm.com>
---
 tools/kvm/kvm_stat/kvm_stat     | 47 +++++++++++++++++++++++++--------
 tools/kvm/kvm_stat/kvm_stat.txt |  4 +++
 2 files changed, 40 insertions(+), 11 deletions(-)

diff --git a/tools/kvm/kvm_stat/kvm_stat b/tools/kvm/kvm_stat/kvm_stat
index 7fe767bd2625..54000ac508f9 100755
--- a/tools/kvm/kvm_stat/kvm_stat
+++ b/tools/kvm/kvm_stat/kvm_stat
@@ -1488,7 +1488,8 @@ def batch(stats):
 
 
 class StdFormat(object):
-    def __init__(self, keys):
+    def __init__(self, keys, skip_zero_records):
+        self._skip_zero_records = skip_zero_records
         self._banner = ''
         for key in keys:
             self._banner += key.split(' ')[0] + ' '
@@ -1496,16 +1497,21 @@ class StdFormat(object):
     def get_banner(self):
         return self._banner
 
-    @staticmethod
-    def get_statline(keys, s):
+    def get_statline(self, keys, s):
         res = ''
+        non_zero = False
         for key in keys:
+            if s[key].delta != 0:
+                non_zero = True
             res += ' %9d' % s[key].delta
+        if self._skip_zero_records and not non_zero:
+            return ''
         return res
 
 
 class CSVFormat(object):
-    def __init__(self, keys):
+    def __init__(self, keys, skip_zero_records):
+        self._skip_zero_records = skip_zero_records
         self._banner = 'timestamp'
         self._banner += reduce(lambda res, key: "{},{!s}".format(res,
                                key.split(' ')[0]), keys, '')
@@ -1513,8 +1519,14 @@ class CSVFormat(object):
     def get_banner(self):
         return self._banner
 
-    @staticmethod
-    def get_statline(keys, s):
+    def get_statline(self, keys, s):
+        if self._skip_zero_records:
+            non_zero = False
+            for key in keys:
+                if s[key].delta != 0:
+                    non_zero = True
+            if self._skip_zero_records and not non_zero:
+                return ''
         return reduce(lambda res, key: "{},{!s}".format(res, s[key].delta),
                       keys, '')
 
@@ -1523,14 +1535,20 @@ def log(stats, opts, frmt, keys):
     """Prints statistics as reiterating key block, multiple value blocks."""
     line = 0
     banner_repeat = 20
+    banner_printed = False
+
     while True:
         try:
             time.sleep(opts.set_delay)
-            if line % banner_repeat == 0:
+            if line % banner_repeat == 0 and not banner_printed:
                 print(frmt.get_banner())
-            print(datetime.now().strftime("%Y-%m-%d %H:%M:%S") +
-                  frmt.get_statline(keys, stats.get()))
+                banner_printed = True
+            statline = frmt.get_statline(keys, stats.get())
+            if len(statline) == 0:
+                continue
+            print(datetime.now().strftime("%Y-%m-%d %H:%M:%S") + statline)
             line += 1
+            banner_printed = False
         except KeyboardInterrupt:
             break
 
@@ -1651,9 +1669,16 @@ Press any other key to refresh statistics immediately.
                            default=False,
                            help='retrieve statistics from tracepoints',
                            )
+    argparser.add_argument('-z', '--skip-zero-records',
+                           action='store_true',
+                           default=False,
+                           help='omit records with all zeros in logging mode',
+                           )
     options = argparser.parse_args()
     if options.csv and not options.log:
         sys.exit('Error: Option -c/--csv requires -l/--log')
+    if options.skip_zero_records and not options.log:
+        sys.exit('Error: Option -z/--skip-zero-records requires -l/--log')
     try:
         # verify that we were passed a valid regex up front
         re.compile(options.fields)
@@ -1736,9 +1761,9 @@ def main():
     if options.log:
         keys = sorted(stats.get().keys())
         if options.csv:
-            frmt = CSVFormat(keys)
+            frmt = CSVFormat(keys, options.skip_zero_records)
         else:
-            frmt = StdFormat(keys)
+            frmt = StdFormat(keys, options.skip_zero_records)
         log(stats, options, frmt, keys)
     elif not options.once:
         with Tui(stats, options) as tui:
diff --git a/tools/kvm/kvm_stat/kvm_stat.txt b/tools/kvm/kvm_stat/kvm_stat.txt
index a97ded2aedad..24296dccc00a 100644
--- a/tools/kvm/kvm_stat/kvm_stat.txt
+++ b/tools/kvm/kvm_stat/kvm_stat.txt
@@ -104,6 +104,10 @@ OPTIONS
 --tracepoints::
         retrieve statistics from tracepoints
 
+*z*::
+--skip-zero-records::
+        omit records with all zeros in logging mode
+
 SEE ALSO
 --------
 'perf'(1), 'trace-cmd'(1)
-- 
2.17.1

[PATCH 2/3] tools/kvm_stat: Add command line switch '-L' to log to file

[Stefan Raspl]

From: Stefan Raspl <raspl@de.ibm.com>

To integrate with logrotate, we have a signal handler that will re-open
the logfile.
Assuming we have a systemd unit file with
     ExecStart=kvm_stat -dtc -s 10 -L /var/log/kvm_stat.csv
     ExecReload=/bin/kill -HUP $MAINPID
and a logrotate config featuring
     postrotate
        /bin/systemctl restart kvm_stat.service
     endscript
Then the overall flow will look like this:
(1) systemd starts kvm_stat, logging to A.
(2) At some point, logrotate runs, moving A to B.
    kvm_stat continues to write to B at this point.
(3) After rotating, logrotate restarts the kvm_stat unit via systemctl.
(4) The kvm_stat unit sends a SIGHUP to kvm_stat, finally making it
    switch over to writing to A again.
Note that in order to keep the structure of the cvs output in tact, we
make sure to, in contrast to the standard log format, only write the
header once at the beginning of a file. This implies that the header is
suppressed when appending to an existing file. Unlike the standard
format, where we append to an existing file by starting out with a
header.

Signed-off-by: Stefan Raspl <raspl@linux.ibm.com>
---
 tools/kvm/kvm_stat/kvm_stat     | 75 +++++++++++++++++++++++++++++----
 tools/kvm/kvm_stat/kvm_stat.txt |  5 +++
 2 files changed, 71 insertions(+), 9 deletions(-)

diff --git a/tools/kvm/kvm_stat/kvm_stat b/tools/kvm/kvm_stat/kvm_stat
index 54000ac508f9..e4f67f0629ee 100755
--- a/tools/kvm/kvm_stat/kvm_stat
+++ b/tools/kvm/kvm_stat/kvm_stat
@@ -32,6 +32,7 @@ import resource
 import struct
 import re
 import subprocess
+import signal
 from collections import defaultdict, namedtuple
 from functools import reduce
 from datetime import datetime
@@ -228,6 +229,8 @@ IOCTL_NUMBERS = {
     'RESET':       0x00002403,
 }
 
+signal_received = False
+
 ENCODING = locale.getpreferredencoding(False)
 TRACE_FILTER = re.compile(r'^[^\(]*$')
 
@@ -1533,25 +1536,73 @@ class CSVFormat(object):
 
 def log(stats, opts, frmt, keys):
     """Prints statistics as reiterating key block, multiple value blocks."""
+    global signal_received
     line = 0
     banner_repeat = 20
-    banner_printed = False
+    f = None
+
+    def do_banner(opts):
+        nonlocal f
+        if opts.log_to_file:
+            if not f:
+                try:
+                     f = open(opts.log_to_file, 'a')
+                except (IOError, OSError):
+                    sys.exit("Error: Could not open file: %s" %
+                             opts.log_to_file)
+                if isinstance(frmt, CSVFormat) and f.tell() != 0:
+                    return
+            f.write(frmt.get_banner())
+            f.write('\n')
+        else:
+            print(frmt.get_banner())
+
+    def do_statline(opts):
+        statline = frmt.get_statline(keys, stats.get())
+        if len(statline) == 0:
+            return False
+        statline = datetime.now().strftime("%Y-%m-%d %H:%M:%S") + statline
+        if opts.log_to_file:
+            f.write(statline)
+            f.write('\n')
+        else:
+            print(statline)
 
+        return True
+
+    do_banner(opts)
+    banner_printed = True
     while True:
         try:
             time.sleep(opts.set_delay)
-            if line % banner_repeat == 0 and not banner_printed:
-                print(frmt.get_banner())
+            if signal_received:
+                banner_printed = True
+                line = 0
+                f.close()
+                do_banner(opts)
+                signal_received = False
+            if (line % banner_repeat == 0 and not banner_printed and
+                not (opts.log_to_file and isinstance(frmt, CSVFormat))):
+                do_banner(opts)
                 banner_printed = True
-            statline = frmt.get_statline(keys, stats.get())
-            if len(statline) == 0:
+            if not do_statline(opts):
                 continue
-            print(datetime.now().strftime("%Y-%m-%d %H:%M:%S") + statline)
             line += 1
             banner_printed = False
         except KeyboardInterrupt:
             break
 
+    if opts.log_to_file:
+        f.close()
+
+
+def handle_signal(sig, frame):
+    global signal_received
+
+    signal_received = True
+
+    return
+
 
 def is_delay_valid(delay):
     """Verify delay is in valid value range."""
@@ -1652,6 +1703,10 @@ Press any other key to refresh statistics immediately.
                            default=False,
                            help='run in logging mode (like vmstat)',
                            )
+    argparser.add_argument('-L', '--log-to-file',
+                           type=str,
+                           help="like '--log', but logging to a file"
+                           )
     argparser.add_argument('-p', '--pid',
                            type=int,
                            default=0,
@@ -1675,9 +1730,9 @@ Press any other key to refresh statistics immediately.
                            help='omit records with all zeros in logging mode',
                            )
     options = argparser.parse_args()
-    if options.csv and not options.log:
+    if options.csv and not (options.log or options.log_to_file):
         sys.exit('Error: Option -c/--csv requires -l/--log')
-    if options.skip_zero_records and not options.log:
+    if options.skip_zero_records and not (options.log or options.log_to_file):
         sys.exit('Error: Option -z/--skip-zero-records requires -l/--log')
     try:
         # verify that we were passed a valid regex up front
@@ -1758,7 +1813,9 @@ def main():
         sys.stdout.write('  ' + '\n  '.join(sorted(set(event_list))) + '\n')
         sys.exit(0)
 
-    if options.log:
+    if options.log or options.log_to_file:
+        if options.log_to_file:
+            signal.signal(signal.SIGHUP, handle_signal)
         keys = sorted(stats.get().keys())
         if options.csv:
             frmt = CSVFormat(keys, options.skip_zero_records)
diff --git a/tools/kvm/kvm_stat/kvm_stat.txt b/tools/kvm/kvm_stat/kvm_stat.txt
index 24296dccc00a..de7c4a2497f9 100644
--- a/tools/kvm/kvm_stat/kvm_stat.txt
+++ b/tools/kvm/kvm_stat/kvm_stat.txt
@@ -92,6 +92,11 @@ OPTIONS
 --log::
         run in logging mode (like vmstat)
 
+
+-L::
+--log-to-file::
+        like '--log', but logging to a file
+
 -p<pid>::
 --pid=<pid>::
 	limit statistics to one virtual machine (pid)
-- 
2.17.1

[PATCH 3/3] tools/kvm_stat: add sample systemd unit file

[Stefan Raspl]

From: Stefan Raspl <raspl@de.ibm.com>

Add a sample unit file as a basis for systemd integration of kvm_stat
logs.

Signed-off-by: Stefan Raspl <raspl@linux.ibm.com>
---
 tools/kvm/kvm_stat/kvm_stat.service | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)
 create mode 100644 tools/kvm/kvm_stat/kvm_stat.service

diff --git a/tools/kvm/kvm_stat/kvm_stat.service b/tools/kvm/kvm_stat/kvm_stat.service
new file mode 100644
index 000000000000..71aabaffe779
--- /dev/null
+++ b/tools/kvm/kvm_stat/kvm_stat.service
@@ -0,0 +1,16 @@
+# SPDX-License-Identifier: GPL-2.0-only
+
+[Unit]
+Description=Service that logs KVM kernel module trace events
+Before=qemu-kvm.service
+
+[Service]
+Type=simple
+ExecStart=/usr/bin/kvm_stat -dtcz -s 10 -L /var/log/kvm_stat.csv
+ExecReload=/bin/kill -HUP $MAINPID
+Restart=always
+SyslogIdentifier=kvm_stat
+SyslogLevel=debug
+
+[Install]
+WantedBy=multi-user.target
-- 
2.17.1

Re: [PATCH 2/3] tools/kvm_stat: Add command line switch '-L' to log to file

[Paolo Bonzini]

On 31/03/20 22:00, Stefan Raspl wrote:
> From: Stefan Raspl <raspl@de.ibm.com>
> 
> To integrate with logrotate, we have a signal handler that will re-open
> the logfile.
> Assuming we have a systemd unit file with
>      ExecStart=kvm_stat -dtc -s 10 -L /var/log/kvm_stat.csv
>      ExecReload=/bin/kill -HUP $MAINPID
> and a logrotate config featuring
>      postrotate
>         /bin/systemctl restart kvm_stat.service

Does reload work too?

Regarding the code, I only have a few nits.


> +            f.write(frmt.get_banner())
> +            f.write('\n')
> +        else:
> +            print(frmt.get_banner())

What about

      print(frmt.get_banner(), file=f or sys.stdout)

> +
> +    def do_statline(opts):
> +        statline = frmt.get_statline(keys, stats.get())
> +        if len(statline) == 0:
> +            return False
> +        statline = datetime.now().strftime("%Y-%m-%d %H:%M:%S") + statline
> +        if opts.log_to_file:
> +            f.write(statline)
> +            f.write('\n')
> +        else:
> +            print(statline)

... and likewise here?  (

>  
> +        return True
> +
> +    do_banner(opts)
> +    banner_printed = True
>      while True:
>          try:
>              time.sleep(opts.set_delay)
> -            if line % banner_repeat == 0 and not banner_printed:
> -                print(frmt.get_banner())
> +            if signal_received:
> +                banner_printed = True
> +                line = 0
> +                f.close()
> +                do_banner(opts)
> +                signal_received = False
> +            if (line % banner_repeat == 0 and not banner_printed and
> +                not (opts.log_to_file and isinstance(frmt, CSVFormat))):
> +                do_banner(opts)
>                  banner_printed = True
> -            statline = frmt.get_statline(keys, stats.get())
> -            if len(statline) == 0:
> +            if not do_statline(opts):
>                  continue
> -            print(datetime.now().strftime("%Y-%m-%d %H:%M:%S") + statline)
>              line += 1
>              banner_printed = False
>          except KeyboardInterrupt:
>              break
>  
> +    if opts.log_to_file:
> +        f.close()

"if f:"?

> +
> +
> +def handle_signal(sig, frame):
> +    global signal_received
> +
> +    signal_received = True
> +
> +    return
> +
>  
>  def is_delay_valid(delay):
>      """Verify delay is in valid value range."""
> @@ -1652,6 +1703,10 @@ Press any other key to refresh statistics immediately.
>                             default=False,
>                             help='run in logging mode (like vmstat)',
>                             )
> +    argparser.add_argument('-L', '--log-to-file',
> +                           type=str,
> +                           help="like '--log', but logging to a file"
> +                           )
>      argparser.add_argument('-p', '--pid',
>                             type=int,
>                             default=0,
> @@ -1675,9 +1730,9 @@ Press any other key to refresh statistics immediately.
>                             help='omit records with all zeros in logging mode',
>                             )
>      options = argparser.parse_args()
> -    if options.csv and not options.log:
> +    if options.csv and not (options.log or options.log_to_file):
>          sys.exit('Error: Option -c/--csv requires -l/--log')

"requires -l/-L"?

> -    if options.skip_zero_records and not options.log:
> +    if options.skip_zero_records and not (options.log or options.log_to_file):
>          sys.exit('Error: Option -z/--skip-zero-records requires -l/--log')

Likewise.

>      try:
>          # verify that we were passed a valid regex up front
> @@ -1758,7 +1813,9 @@ def main():
>          sys.stdout.write('  ' + '\n  '.join(sorted(set(event_list))) + '\n')
>          sys.exit(0)
>  
> -    if options.log:
> +    if options.log or options.log_to_file:
> +        if options.log_to_file:
> +            signal.signal(signal.SIGHUP, handle_signal)
>          keys = sorted(stats.get().keys())
>          if options.csv:
>              frmt = CSVFormat(keys, options.skip_zero_records)
> diff --git a/tools/kvm/kvm_stat/kvm_stat.txt b/tools/kvm/kvm_stat/kvm_stat.txt
> index 24296dccc00a..de7c4a2497f9 100644
> --- a/tools/kvm/kvm_stat/kvm_stat.txt
> +++ b/tools/kvm/kvm_stat/kvm_stat.txt
> @@ -92,6 +92,11 @@ OPTIONS
>  --log::
>          run in logging mode (like vmstat)
>  
> +
> +-L::
> +--log-to-file::
> +        like '--log', but logging to a file

-L<file>:: / --log-to-file=<file>

> +
>  -p<pid>::
>  --pid=<pid>::
>  	limit statistics to one virtual machine (pid)
> 

Re: [PATCH 1/3] tools/kvm_stat: add command line switch '-z' to skip zero records

[Paolo Bonzini]

On 31/03/20 22:00, Stefan Raspl wrote:
> @@ -1523,14 +1535,20 @@ def log(stats, opts, frmt, keys):
>      """Prints statistics as reiterating key block, multiple value blocks."""
>      line = 0
>      banner_repeat = 20
> +    banner_printed = False
> +
>      while True:
>          try:
>              time.sleep(opts.set_delay)
> -            if line % banner_repeat == 0:
> +            if line % banner_repeat == 0 and not banner_printed:
>                  print(frmt.get_banner())
> -            print(datetime.now().strftime("%Y-%m-%d %H:%M:%S") +
> -                  frmt.get_statline(keys, stats.get()))
> +                banner_printed = True

Can't skip_zero_records be handled here instead?

    values = stats.get()
    if not opts.skip_zero_records or \
        any((values[k].delta != 0 for k in keys):
       statline = frmt.get_statline(keys, values)
       print(datetime.now().strftime("%Y-%m-%d %H:%M:%S") + statline)

Paolo

> +            print(datetime.now().strftime("%Y-%m-%d %H:%M:%S") + statline)
>              line += 1

Re: [PATCH 1/3] tools/kvm_stat: add command line switch '-z' to skip zero records

[Stefan Raspl]

On 2020-03-31 23:45, Paolo Bonzini wrote:
> On 31/03/20 22:00, Stefan Raspl wrote:
>> @@ -1523,14 +1535,20 @@ def log(stats, opts, frmt, keys):
>>      """Prints statistics as reiterating key block, multiple value blocks."""
>>      line = 0
>>      banner_repeat = 20
>> +    banner_printed = False
>> +
>>      while True:
>>          try:
>>              time.sleep(opts.set_delay)
>> -            if line % banner_repeat == 0:
>> +            if line % banner_repeat == 0 and not banner_printed:
>>                  print(frmt.get_banner())
>> -            print(datetime.now().strftime("%Y-%m-%d %H:%M:%S") +
>> -                  frmt.get_statline(keys, stats.get()))
>> +                banner_printed = True
> 
> Can't skip_zero_records be handled here instead?
> 
>     values = stats.get()
>     if not opts.skip_zero_records or \
>         any((values[k].delta != 0 for k in keys):
>        statline = frmt.get_statline(keys, values)
>        print(datetime.now().strftime("%Y-%m-%d %H:%M:%S") + statline)

I wanted to avoid such an extra check for performance reasons. Granted, I have
to do something likewise (i.e. checking for non-zero values) in my patch for csv
records, but at least for the standard format things are a bit less costly
(avoiding an extra pass over the data).

Ciao,
Stefan

Re: [PATCH 2/3] tools/kvm_stat: Add command line switch '-L' to log to file

[Stefan Raspl]

On 2020-03-31 23:02, Paolo Bonzini wrote:
> On 31/03/20 22:00, Stefan Raspl wrote:
>> From: Stefan Raspl <raspl@de.ibm.com>
>>
>> To integrate with logrotate, we have a signal handler that will re-open
>> the logfile.
>> Assuming we have a systemd unit file with
>>      ExecStart=kvm_stat -dtc -s 10 -L /var/log/kvm_stat.csv
>>      ExecReload=/bin/kill -HUP $MAINPID
>> and a logrotate config featuring
>>      postrotate
>>         /bin/systemctl restart kvm_stat.service
> 
> Does reload work too?

Reload and restart work fine - any specific concerns or areas to look for?


> Regarding the code, I only have a few nits.
> 
> 
>> +            f.write(frmt.get_banner())
>> +            f.write('\n')
>> +        else:
>> +            print(frmt.get_banner())
> 
> What about
> 
>       print(frmt.get_banner(), file=f or sys.stdout)

Yup, thx!


>> +
>> +    def do_statline(opts):
>> +        statline = frmt.get_statline(keys, stats.get())
>> +        if len(statline) == 0:
>> +            return False
>> +        statline = datetime.now().strftime("%Y-%m-%d %H:%M:%S") + statline
>> +        if opts.log_to_file:
>> +            f.write(statline)
>> +            f.write('\n')
>> +        else:
>> +            print(statline)
> 
> ... and likewise here?  (

Sure


>>  
>> +        return True
>> +
>> +    do_banner(opts)
>> +    banner_printed = True
>>      while True:
>>          try:
>>              time.sleep(opts.set_delay)
>> -            if line % banner_repeat == 0 and not banner_printed:
>> -                print(frmt.get_banner())
>> +            if signal_received:
>> +                banner_printed = True
>> +                line = 0
>> +                f.close()
>> +                do_banner(opts)
>> +                signal_received = False
>> +            if (line % banner_repeat == 0 and not banner_printed and
>> +                not (opts.log_to_file and isinstance(frmt, CSVFormat))):
>> +                do_banner(opts)
>>                  banner_printed = True
>> -            statline = frmt.get_statline(keys, stats.get())
>> -            if len(statline) == 0:
>> +            if not do_statline(opts):
>>                  continue
>> -            print(datetime.now().strftime("%Y-%m-%d %H:%M:%S") + statline)
>>              line += 1
>>              banner_printed = False
>>          except KeyboardInterrupt:
>>              break
>>  
>> +    if opts.log_to_file:
>> +        f.close()
> 
> "if f:"?

I'd argue the former is a lot more telling/easier to read - one of the downsides
of using extremely short variable names like 'f'.


>> +
>> +
>> +def handle_signal(sig, frame):
>> +    global signal_received
>> +
>> +    signal_received = True
>> +
>> +    return
>> +
>>  
>>  def is_delay_valid(delay):
>>      """Verify delay is in valid value range."""
>> @@ -1652,6 +1703,10 @@ Press any other key to refresh statistics immediately.
>>                             default=False,
>>                             help='run in logging mode (like vmstat)',
>>                             )
>> +    argparser.add_argument('-L', '--log-to-file',
>> +                           type=str,
>> +                           help="like '--log', but logging to a file"
>> +                           )
>>      argparser.add_argument('-p', '--pid',
>>                             type=int,
>>                             default=0,
>> @@ -1675,9 +1730,9 @@ Press any other key to refresh statistics immediately.
>>                             help='omit records with all zeros in logging mode',
>>                             )
>>      options = argparser.parse_args()
>> -    if options.csv and not options.log:
>> +    if options.csv and not (options.log or options.log_to_file):
>>          sys.exit('Error: Option -c/--csv requires -l/--log')
> 
> "requires -l/-L"?

Yes!


>> -    if options.skip_zero_records and not options.log:
>> +    if options.skip_zero_records and not (options.log or options.log_to_file):
>>          sys.exit('Error: Option -z/--skip-zero-records requires -l/--log')
> 
> Likewise.

Of course.


>>      try:
>>          # verify that we were passed a valid regex up front
>> @@ -1758,7 +1813,9 @@ def main():
>>          sys.stdout.write('  ' + '\n  '.join(sorted(set(event_list))) + '\n')
>>          sys.exit(0)
>>  
>> -    if options.log:
>> +    if options.log or options.log_to_file:
>> +        if options.log_to_file:
>> +            signal.signal(signal.SIGHUP, handle_signal)
>>          keys = sorted(stats.get().keys())
>>          if options.csv:
>>              frmt = CSVFormat(keys, options.skip_zero_records)
>> diff --git a/tools/kvm/kvm_stat/kvm_stat.txt b/tools/kvm/kvm_stat/kvm_stat.txt
>> index 24296dccc00a..de7c4a2497f9 100644
>> --- a/tools/kvm/kvm_stat/kvm_stat.txt
>> +++ b/tools/kvm/kvm_stat/kvm_stat.txt
>> @@ -92,6 +92,11 @@ OPTIONS
>>  --log::
>>          run in logging mode (like vmstat)
>>  
>> +
>> +-L::
>> +--log-to-file::
>> +        like '--log', but logging to a file
> 
> -L<file>:: / --log-to-file=<file>

Argh...

Ciao,
Stefan

Re: [PATCH 1/3] tools/kvm_stat: add command line switch '-z' to skip zero records

[Paolo Bonzini]

On 01/04/20 10:19, Stefan Raspl wrote:
> On 2020-03-31 23:45, Paolo Bonzini wrote:
>> On 31/03/20 22:00, Stefan Raspl wrote:
>>> @@ -1523,14 +1535,20 @@ def log(stats, opts, frmt, keys):
>>>      """Prints statistics as reiterating key block, multiple value blocks."""
>>>      line = 0
>>>      banner_repeat = 20
>>> +    banner_printed = False
>>> +
>>>      while True:
>>>          try:
>>>              time.sleep(opts.set_delay)
>>> -            if line % banner_repeat == 0:
>>> +            if line % banner_repeat == 0 and not banner_printed:
>>>                  print(frmt.get_banner())
>>> -            print(datetime.now().strftime("%Y-%m-%d %H:%M:%S") +
>>> -                  frmt.get_statline(keys, stats.get()))
>>> +                banner_printed = True
>>
>> Can't skip_zero_records be handled here instead?
>>
>>     values = stats.get()
>>     if not opts.skip_zero_records or \
>>         any((values[k].delta != 0 for k in keys):
>>        statline = frmt.get_statline(keys, values)
>>        print(datetime.now().strftime("%Y-%m-%d %H:%M:%S") + statline)
> 
> I wanted to avoid such an extra check for performance reasons. Granted, I have
> to do something likewise (i.e. checking for non-zero values) in my patch for csv
> records, but at least for the standard format things are a bit less costly
> (avoiding an extra pass over the data).

I don't think it's a perceivable difference, and it simplifies the code
noticeably.

Paolo

Re: [PATCH 2/3] tools/kvm_stat: Add command line switch '-L' to log to file

[Paolo Bonzini]

On 01/04/20 14:59, Stefan Raspl wrote:
> On 2020-03-31 23:02, Paolo Bonzini wrote:
>> On 31/03/20 22:00, Stefan Raspl wrote:
>>> From: Stefan Raspl <raspl@de.ibm.com>
>>>
>>> To integrate with logrotate, we have a signal handler that will re-open
>>> the logfile.
>>> Assuming we have a systemd unit file with
>>>      ExecStart=kvm_stat -dtc -s 10 -L /var/log/kvm_stat.csv
>>>      ExecReload=/bin/kill -HUP $MAINPID
>>> and a logrotate config featuring
>>>      postrotate
>>>         /bin/systemctl restart kvm_stat.service
>>
>> Does reload work too?
> 
> Reload and restart work fine - any specific concerns or areas to look for?

No, I would just put reload in the postrotate script.
>>> +    if opts.log_to_file:
>>> +        f.close()
>>
>> "if f:"?
> 
> I'd argue the former is a lot more telling/easier to read - one of the downsides
> of using extremely short variable names like 'f'.

Fair enough.

Paolo