[rrd-developers] MSYNC issues

AJ Ragusa aragusa at grnoc.iu.edu
Mon Nov 10 22:16:13 CET 2008

Hi Guys

I have been using RRDTool 1.3.3 for a few months now without a  
problem, until one of my users noticed that on NFS mounts the rrdfiles  
were not updating.... after a full day of scratching my head and  
swearing about NFS I finally noticed that the last modified date of  
the files was not updating and was the cause of my NFS problems.

Further investigation finally led me to this kernel bug


I was slightly disheartened by one of the last posts

------- Comment  #49 From Anton Salikhmetov  2008-01-23 15:10:11   
[reply] -------

The patch applied to the upstream kernel fixes this bug. Closing.

The remaining problem is to satisfy the paper standard requirement. This
requirement is totally ambiguous and requires invasive changes and  
code. This is the MS_ASYNC case of the msync() function. Googling  
shows that
the msync() function is most probably not called with the MS_ASYNC  
flag by any
popular application. Therefore, it is left unimplemented for now.


After I looked through the RRDTool code I found that it is using the  
MS_ASYNC flag... since this problem was only recently resolved (only  
took 4 years) in January of 2008 I'm guessing that not a lot of  
kernels have this fix.  Is it ok to change to MS_SYNC for the flag to  
msynch instead of MS_ASYNC?  Or is that going to cause more problems?

Has anyone else seen any problems related to this, and have a fix?

A.J. Ragusa
System Engineer - Global Research Network Operations Center

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