Driver for SSD devices that support NVMe (Non-Volatile Memory Express)
Note:
In order to start this driver, you must be logged in as root or have the right abilities.
Syntax:
devb-nvme [cam option[,option]...]
[mem option[,option]...]
[nvme options[,option]...]
Options:
Note:
Use commas (,) to separate the options.
You can put the blk, cam, disk, and umass
groups of options in any order.
- blk options
- The blk options control the
io-blk.so driver.
If specified, they must follow the blk keyword.
- cam options
- The cam options control
libcam.so.
If specified, they must follow the cam keyword.
- mem options
-
- name=tname
- The typed memory name to use.
This option lets you restrict the driver to use memory only from a particular region, which is often necessary for
DMA and smmuman. If you set this option, it can benefit performance to set the same option in the
blk layer as well, depending on the size of the typed memory region.
The cam layer will move data between the blk layer and the typed memory.
Note:
It's up to the startup to set up typed memory.
For more information, see
“Typed memory”
in the
“Interprocess Communication (IPC)” chapter of the
System Architecture guide.
- nvme options
- The nvme options control the driver's interface to the NVMe device.
If you've installed multiple devices, you can repeat these options
for each device. Remember, however, to specify the nvme keyword
before each controller's set of options.
- aev=state
- Enable or disable asynchronous events. The default is enabled.
- apst=latency, state
- Set the latency to enable or disable the autonomous power state
transition maximum latency. The default is 100ms, enabled.
- depth=num
- Set the queue depth, which is the maximum number of commands per queue.
The driver's default setting of 16 is used if you don't set this option or you
provide an invalid or out-of-range value. (The range is between 1 and 65535.)
When you provide a valid, in-range value, the driver checks your accepted value
against the capabilities reported by the hardware and uses the smaller queue depth
value, as in this expression: min( num,
hardware_depth )
- did=did
- The device ID of the device.
- hmb=state
- Enable or disable the host memory buffer. The default is enabled.
- icoalesce=time:
threshold,
state
- Set and enable interrupt coalescing. Default is 100us:2, disabled
- ioport=addr
- The address of the interface. There is no default value.
- irq=interrupt
- The interrupt used by the controller.
- pci=index
- The PCI index of the controller in the machine, where
index is a value between 0 and the number of adapters.
There is no default value for this option.
- queues=num
- Set the number of queues.
The driver's default setting of 32 is used if you don't set this option or you
provide an invalid or out-of-range value. (The range is between 1 and 65535.)
Most likely, you want to limit the number of queues to the number of cores/CPUs
on your system (e.g., 1, 2, or 4). When you provide a valid, in-range value, the
driver checks your accepted value against the capabilities reported by the hardware
and uses the smaller queue number value, as in this expression:
min( num, hardware_queues )
- vid=vid
- The vendor ID of the device.
- wc=state
- Enable or disable the write cache. The default is enabled.
Description:
The devb-nvme driver is the driver for SSD devices that
support the NVMe open logical interface specification for accessing non-volatile
storage media.
Examples:
Start the driver, detecting all NVME controllers, and listing all connected devices:
devb-nvme &