On 06/06/2016 04:00 PM, Karl Cronburg wrote:
Hello, In benchmarking ceph I've been using fio / fiologparser, and want to get out the sort of stats & percentiles fiologparser currently gives (min, avg, max, percentiles). However I'm concerned the data coming out of fio is insufficient when I pass it the log_avg_msec argument. Namely using the average of a possibly asymmetric sample distribution (the set of I/O request samples over which fio is averaging when I pass it this argument) will not give accurate percentiles. Something like this argument is necessary though to keep the log files a reasonable size. Would it be a good idea to push the sort of statistics done in the log parser directly into fio? I'm considering writing some code to compute the quantiles directly in fio, either brute-force by maintaining a sorted list or implementing something like the algorithm described here: http://www.cs.rutgers.edu/~muthu/bquant.pdf with some acceptable user-defined level of error given to fio when asked to compute the percentiles on long-running / large data sets. Is there any interest in having this added directly into fio? If so where in the code should I be looking?
I think it would be great! I confess I haven't read through the paper yet (and may not be able to before I leave on holiday for 2 weeks). The big thing will be having some kind of reasonable test case data to make sure the results are reasonable and an explanation of how it works. It's one of the things missing from fiologparser.py right now.
Potentially this could benefit a lot more folks than just those of us doing ceph testing, so I'd say go for it. :)
-Karl Cronburg- -- To unsubscribe from this list: send the line "unsubscribe fio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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