On 3/16/18 12:45 PM, Jeff Furlong wrote: > A few comments: > > -How does the cpu utilization look compared between the lfsr and > default tausworthe generators? Is the cpu util actually higher on > lfsr? If it is near saturated on 16 devices, then naturally > throughput would decrease. The LFSR generator is constant overhead, and it should not degrade as more jobs are using it. There's no shared state at all. If I were to guess, then the identical offsets of the jobs is probably a likely clue, since that is the only real difference between the two random generators. Are these 16 volumes all completely separate? Finally, you are having 8 jobs all accessing the same 16 devices. You'll likely get more consistent performance if you split things up a bit by having 4 jobs, each doing IO to just two of the disks. This shouldn't really be impacted by the random generator, but your current setup is prone to performance fluctuations. -- Jens Axboe -- 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
