Hi Marcelo, Marcelo Leal wrote: > Sorry, but i do not agree. > We are talking about a NFSv3 provider, and not about how many cpu's there > are on the system. I do not have the knowledge to discuss with you the > aspects about the implementation, but as a user point of view, i think that > numbers don't make sense. If the fact that the number of cpu's is important > for the start/done for the NFS provider, i think it will for all other dtrace > providers. > I have found that almost all "bugs" with dtrace are either in the scripting or in the interpretation of the output. The mechanism used to implement dtrace is quite simple, and for the script you are running, I don't believe you are hitting any bug in the implementation of dtrace. Also, using dtrace to examine the system is like using a microscope. You need to know the big picture first, before you can determine what you need to trace. Otherwise you can end up getting a lot of detail about something that has nothing to do with the problem you are experiencing. In this instance, as Jim says, iostat will give you a better view of the big picture.
As for the 20 minutes total time spent for I/O in a script running 10 minutes, this could happen even on a single CPU. For example, you start the script and immediately 10 I/O requests are made. Now, let's say all 10 requests are queued (i.e., block, waiting for some resource). If they all finish just before the end of the 10 minute period, the total elapsed time would be about 100 minutes. So long as the total time divided by the number of operations does not exceed 10 minutes, the output is reasonable. I suspect the outliers, (the I/Os that are taking 2-4 seconds) are due to queuing at the disk driver, but they could be due to scheduling as well. (I would have to look at exactly when the start and done probes fire to determine this. But fortunately, source code is available to determine this.). As I mentioned in an earlier post, speculative tracing can be used to determine the code path taken for the longest I/O. I have written a script that might work, but have no way to test it at this time. If you are interested, I'll post it. Jim, as for taking this offline, that is ok for you, but my posts to Marcelo are bouncing... max > Thanks a lot for your answers Max! > > __ > Leal > [http://www.eall.com.br/blog] > _______________________________________________ dtrace-discuss mailing list dtrace-discuss@opensolaris.org
