examples/nvme_fio_plugin: update ZNS section of README

Signed-off-by: Simon A. F. Lund <simon.lund@samsung.com>
Change-Id: I99c82490811314201b53dde59e586538835e0840
Reviewed-on: https://review.spdk.io/gerrit/c/spdk/spdk/+/4950
Reviewed-by: Jim Harris <james.r.harris@intel.com>
Reviewed-by: Niklas Cassel <niklas.cassel@wdc.com>
Reviewed-by: Ben Walker <benjamin.walker@intel.com>
Community-CI: Mellanox Build Bot
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
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Simon A. F. Lund 2020-10-28 16:48:22 +01:00 committed by Jim Harris
parent aae84b1f0e
commit f875da4019

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@ -116,3 +116,33 @@ To your fio-script, also have a look at script-examples provided with fio:
fio/examples/zbd-seq-read.fio
fio/examples/zbd-rand-write.fio
## Maximum Open Zones
Zoned Namespaces has a resource constraint on the amount of zones which can be in an opened state at
any point in time. You can control how many zones fio will keep in an open state by using the
``--max_open_zones`` option.
The SPDK/NVMe fio io-engine will set a default value if you do not provide one.
## Maximum Active Zones
Zoned Namespaces has a resource constraint on the number of zones that can be active at any point in
time. Unlike ``max_open_zones``, then fio currently do not manage this constraint, and there is thus
no option to limit it either.
When running with the SPDK/NVMe fio io-engine you can be exposed to error messages, in the form of
completion errors, with the NVMe status code of 0xbd ("Too Many Active Zones"). To work around this,
then you can reset all zones before fio start running its jobs by using the engine option:
--initial_zone_reset=1
## Shared Memory Increase
If your device has a lot of zones, fio can give you errors such as:
smalloc: OOM. Consider using --alloc-size to increase the shared memory available.
This is because fio needs to allocate memory for the zone-report, that is, retrieve the state of
zones on the device including auxiliary accounting information. To solve this, then you can follow
fio's advice and increase ``--alloc-size``.