On 2011-11-09 02:10, Steven Lang wrote: > I noticed that the rate= option is not terribly precise in some cases. > It gets worse the higher the selected rate. For example: > $ fio -name=load -size=100g -ioengine=null -runtime=10 -rate=30m > One would expect that to read 300MB (307200KB) at close to 30MB/s > (30720KB/s). However it writes 315024KB at 31499KB/s. Further > experimentation shows that even higher rates can show bigger > discrepancies. At the extreme end... > $ fio -name=load -size=100g -ioengine=null -runtime=10 -rate=500m > One would expect this to write 5000MB at a rate of 500MB/s > (512000KB/s). However it writes close to double that (9536.8MB) at a > rate of over 953MB/s. At a rate of 1GB/s and higher, the rate > limiting is effectively ignored. > > This patch improves the accuracy of the rate= option across the whole > range of rates, at the cost of being very slightly more > computationally expensive. Thanks Steven, another great patch. Applied. I'm still mulling over the option patch. It'd be great if one could do: $ fio --cmdhelp=ioengine=libaio to display these private options. And it's a bit confusing on the global vs private engine options, but in reality it _probably_ wont bite anyone. Anyway, I fiddle with it a bit and let you know. -- 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
