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List:       linux-nfs
Subject:    Re: [PATCH 1/1] nfs-iostat.py: Fixes several Divide by Zero errors
From:       Kevin Constantine <Kevin.Constantine () disneyanimation ! com>
Date:       2010-05-28 22:51:58
Message-ID: 4C00490E.3030801 () disney ! com
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On 05/28/2010 10:00 AM, Chuck Lever wrote:
> On 05/27/10 08:50 PM, Kevin Constantine wrote:
>> The first time through the code sample_time is set to 0.0 on line 588.
>> Eventually we call display_iostats() and check if sample_time == 0. It
>> does, so we set sample_time equal to the mount age on line 368. I'm
>> seeing instances where the age of a mount is 0.
>>
>> cat /proc/self/mountstats | egrep "device|age"
>> device fashome-n1:/vol/home/fahome mounted on /home/fahome with fstype
>> nfs statvers=1.0
>> age: 0
>>
>> All of our storage is automounted, so volumes are frequently getting
>> unmounted and remounted.
>
> Makes sense. When I wrote the script, I wasn't using automounter at all.
> It might be simpler to have one check for a zero age at 368.
>

My only concern with checking and just returning (which is certainly 
easier and a smaller change) is that we end up not printing anything for 
a volume that is technically mounted.  I figured it was better to print 
the volume info and all zeroes than to not print anything.

I'll defer to your opinion on which of those two is best.

-kevin

>> On 05/27/2010 05:22 PM, Chuck Lever wrote:
>>> 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:
>>>>
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