Re: [PATCH 1/1] nfs-iostat.py: Fixes several Divide by Zero errors

Chuck Lever <chuck.lever@xxxxxxxxxx> · Thu, 27 May 2010 20:22:17 -0400

On 05/27/2010 07:58 PM, Kevin Constantine wrote:
There was no check to see if sample_time was zero before dividing by it.

I haven't looked at this code in a very long time.  Why was sample_time 
zero?  That seems wrong.

This was causing ZeroDivisionError's:

Traceback (most recent call last):
   File "/home/fahome/kconstan/repos/nfs-utils.upstream/tools/nfs-iostat/nfs-iostat.py", line 628, in ?
     iostat_command(prog)
   File "/home/fahome/kconstan/repos/nfs-utils.upstream/tools/nfs-iostat/nfs-iostat.py", line 610, in iostat_command
     print_iostat_summary(old_mountstats, mountstats, devices, sample_time, options)
   File "/home/fahome/kconstan/repos/nfs-utils.upstream/tools/nfs-iostat/nfs-iostat.py", line 462, in print_iostat_summary
     stats[device].display_iostats(time, options.which)
   File "/home/fahome/kconstan/repos/nfs-utils.upstream/tools/nfs-iostat/nfs-iostat.py", line 370, in display_iostats
     backlog = (float(self.__rpc_data['backlogutil']) / sends) / sample_time
ZeroDivisionError: float division

Traceback (most recent call last):
   File "/home/fahome/kconstan/repos/nfs-utils.upstream/tools/nfs-iostat/nfs-iostat.py", line 628, in ?
     iostat_command(prog)
   File "/home/fahome/kconstan/repos/nfs-utils.upstream/tools/nfs-iostat/nfs-iostat.py", line 610, in iostat_command
     print_iostat_summary(old_mountstats, mountstats, devices, sample_time, options)
   File "/home/fahome/kconstan/repos/nfs-utils.upstream/tools/nfs-iostat/nfs-iostat.py", line 462, in print_iostat_summary
     stats[device].display_iostats(time, options.which)
   File "/home/fahome/kconstan/repos/nfs-utils.upstream/tools/nfs-iostat/nfs-iostat.py", line 380, in display_iostats
     print '%7.2f' % (sends / sample_time),
ZeroDivisionError: float division

Traceback (most recent call last):
   File "/home/fahome/kconstan/repos/nfs-utils.upstream/tools/nfs-iostat/nfs-iostat.py", line 630, in ?
     iostat_command(prog)
   File "/home/fahome/kconstan/repos/nfs-utils.upstream/tools/nfs-iostat/nfs-iostat.py", line 612, in iostat_command
     print_iostat_summary(old_mountstats, mountstats, devices, sample_time, options)
   File "/home/fahome/kconstan/repos/nfs-utils.upstream/tools/nfs-iostat/nfs-iostat.py", line 464, in print_iostat_summary
     stats[device].display_iostats(time, options.which)
   File "/home/fahome/kconstan/repos/nfs-utils.upstream/tools/nfs-iostat/nfs-iostat.py", line 386, in display_iostats
     self.__print_rpc_op_stats('READ', sample_time)
   File "/home/fahome/kconstan/repos/nfs-utils.upstream/tools/nfs-iostat/nfs-iostat.py", line 350, in __print_rpc_op_stats
     print '\t\t%7.3f' % (ops / sample_time),
ZeroDivisionError: float division

Signed-off-by: Kevin Constantine<kevin.constantine@xxxxxxxxxxxxxxxxxxx>
---
  tools/nfs-iostat/nfs-iostat.py |   20 +++++++++++++++-----
  1 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/tools/nfs-iostat/nfs-iostat.py b/tools/nfs-iostat/nfs-iostat.py
index 2d0b143..4d6b295 100644
--- a/tools/nfs-iostat/nfs-iostat.py
+++ b/tools/nfs-iostat/nfs-iostat.py
@@ -342,13 +342,19 @@ class DeviceData:
              retrans_percent = 0.0
              rtt_per_op = 0.0
              exe_per_op = 0.0
+        if sample_time != 0:
+            ops_per_sample_time = ops / sample_time
+            kb_per_sample_time = kilobytes / sample_time
+        else:
+            ops_per_sample_time = 0.0
+            kb_per_sample_time = 0.0

          op += ':'
          print '%s' % op.lower().ljust(15),
          print '  ops/s\t\t   kB/s\t\t  kB/op\t\tretrans\t\tavg RTT (ms)\tavg exe (ms)'

-        print '\t\t%7.3f' % (ops / sample_time),
-        print '\t%7.3f' % (kilobytes / sample_time),
+        print '\t\t%7.3f' % (ops_per_sample_time),
+        print '\t%7.3f' % (kb_per_sample_time),
          print '\t%7.3f' % kb_per_op,
          print ' %7d (%3.1f%%)' % (retrans, retrans_percent),
          print '\t%7.3f' % rtt_per_op,
@@ -358,7 +364,9 @@ class DeviceData:
          sends = float(self.__rpc_data['rpcsends'])
          if sample_time == 0:
              sample_time = float(self.__nfs_data['age'])
-        return (sends / sample_time)
+            return (sends / sample_time)
+        else:
+            return(0.0)

      def display_iostats(self, sample_time, which):
          """Display NFS and RPC stats in an iostat-like way
@@ -366,10 +374,12 @@ class DeviceData:
          sends = float(self.__rpc_data['rpcsends'])
          if sample_time == 0:
              sample_time = float(self.__nfs_data['age'])
-        if sends != 0:
+        if sends != 0 and sample_time != 0:
              backlog = (float(self.__rpc_data['backlogutil']) / sends) / sample_time
+            sends_per_sample_time = sends / sample_time
          else:
              backlog = 0.0
+            sends_per_sample_time = 0.0

          print
          print '%s mounted on %s:' % \
@@ -377,7 +387,7 @@ class DeviceData:
          print

          print '   op/s\t\trpc bklog'
-        print '%7.2f' % (sends / sample_time),
+        print '%7.2f' % (sends_per_sample_time),
          print '\t%7.2f' % backlog

          if which == 0:


--
chuck[dot]lever[at]oracle[dot]com
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