On 11/20/2015 12:37 PM, Caio Villela wrote:
Hello Allen and Jens, Sorry for the long output, this is just in case you want the details. Here is a simple explanation for the problem. I want to run a 15 minute random write, using 1 Meg requests, and measure throughput and latency. What seems to be the problem is that if the test system has a large number of drives - the system that I am testing here has 28 drives - then the time accounting seems to go bad for some of the processes. What you see below is that during the 15 minutes from start, all disks are getting hit the same, as they should. Then, after 15 minutes, there are 15 drives that are still running.... after 5 minutes over the specified 15 minutes, there is still one drive running. Then looking at the amount of IOs sent to each drive, the ones that ran on that excess time have much more IOs. FIO still reports that all drives ran for 15 minutes, although some ran for more than 20 minutes. We will attempt to run a single process instead of 28 instances of FIO to see if this goes away.
Could you also check if adding clocksource=gettimeofday makes any difference? This sounds very odd.
Assuming this was run with fio -git? -- 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
