question on fio memory handling

question on fio memory handling

[Paolo Valente]

Hi,
we are using fio to generate interleaved I/O, by making several job read from the whole /dev/sda and we are using zoneskip to create the interleave among jobs.

But we have bumped into the following issue, shown for just one job. The following command:

$ sudo fio --name=reader0 -rw=read --filename=/dev/sda --zonesize=16384 --zonemode=zbd --zoneskip=16384
smalloc: OOM. Consider using --alloc-size to increase the shared memory available.

In contrast, if we invoke,

sudo fio --name=reader0 -rw=read --filename=/dev/sda --zonesize=16384 --zonemode=strided --zoneskip=16384

(which is ok for our goal at the moment), then we everything seems to work fine.

Could you please example me why --zonemode=zbd fails by apparently trying to allocate memory for the whole size of the special file /dev/sda? Is it (strictly) necessary for doing random I/O among zones?

Thanks,
Paolo