(I know this one is old but I seem to have had a reply rolling around in my draft folder for a while) On 29 January 2018 at 16:45, weiping zhang <zhangweiping@xxxxxxxxxxxxxxx> wrote: > If user want control the inflight IOs for the tested block device, for > example set iodepth=16, and we can get result like following: > > IO depths: 1=0.1%, 2=0.1%, 4=0.1%, 8=0.1%, 16=100.0%, 32=0.0%, >=64=0.0% > > this result only means (16~31) IOs inflight, don't means requests inflight, > if max_sectors_kb = 64KB, and we set bs=256KB, the number of inflight > requests may reach to 64(if nr_request allow). So for user want to control > the number of inflight requests, bs should less than max_sectors_kb. You have a point but that's very Linux platform specific information (then again so is the libaio warning so there's a precedent there already). Additionally, dependent on a device's I/O scheduler and its options etc. just because you submitted smaller blocks doesn't mean those I/Os won't be merged together thus the amount of requests inflight down to a device can still be different to what fio is submitting to the kernel. Further, there may also be different layers in the strack between userspace and the device that transform the I/Os (e.g. md RAID etc.) before they turn into device requests so there are lots of caveats. -- Sitsofe | http://sucs.org/~sits/ -- 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
