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14 .\" including a substantially similar Disclaimer requirement for further
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30 .\" nvme driver man page.
32 .\" Author: Jim Harris <jimharris@FreeBSD.org>
41 .Nd NVM Express core driver
43 To compile this driver into your kernel,
44 place the following line in your kernel configuration file:
45 .Bd -ragged -offset indent
49 Or, to load the driver as a module at boot, place the following line in
51 .Bd -literal -offset indent
55 Most users will also want to enable
57 to expose NVM Express namespaces as disk devices which can be
59 Note that in NVM Express terms, a namespace is roughly equivalent to a
64 driver provides support for NVM Express (NVMe) controllers, such as:
67 Hardware initialization
69 Per-CPU IO queue pairs
71 API for registering NVMe namespace consumers such as
76 API for submitting NVM commands to namespaces
78 Ioctls for controller and namespace configuration and management
83 driver creates controller device nodes in the format
85 and namespace device nodes in
88 Note that the NVM Express specification starts numbering namespaces at 1,
89 not 0, and this driver follows that convention.
93 will create an I/O queue pair for each CPU, provided enough MSI-X vectors
94 and NVMe queue pairs can be allocated.
95 If not enough vectors or queue
96 pairs are available, nvme(4) will use a smaller number of queue pairs and
97 assign multiple CPUs per queue pair.
99 To force a single I/O queue pair shared by all CPUs, set the following
102 .Bd -literal -offset indent
103 hw.nvme.per_cpu_io_queues=0
106 To assign more than one CPU per I/O queue pair, thereby reducing the number
107 of MSI-X vectors consumed by the device, set the following tunable value in
109 .Bd -literal -offset indent
110 hw.nvme.min_cpus_per_ioq=X
113 To force legacy interrupts for all
115 driver instances, set the following tunable value in
117 .Bd -literal -offset indent
121 Note that use of INTx implies disabling of per-CPU I/O queue pairs.
123 The following controller-level sysctls are currently implemented:
124 .Bl -tag -width indent
125 .It Va dev.nvme.0.num_cpus_per_ioq
126 (R) Number of CPUs associated with each I/O queue pair.
127 .It Va dev.nvme.0.int_coal_time
128 (R/W) Interrupt coalescing timer period in microseconds.
130 .It Va dev.nvme.0.int_coal_threshold
131 (R/W) Interrupt coalescing threshold in number of command completions.
135 The following queue pair-level sysctls are currently implemented.
136 Admin queue sysctls take the format of dev.nvme.0.adminq and I/O queue sysctls
137 take the format of dev.nvme.0.ioq0.
138 .Bl -tag -width indent
139 .It Va dev.nvme.0.ioq0.num_entries
140 (R) Number of entries in this queue pair's command and completion queue.
141 .It Va dev.nvme.0.ioq0.num_tr
142 (R) Number of nvme_tracker structures currently allocated for this queue pair.
143 .It Va dev.nvme.0.ioq0.num_prp_list
144 (R) Number of nvme_prp_list structures currently allocated for this queue pair.
145 .It Va dev.nvme.0.ioq0.sq_head
146 (R) Current location of the submission queue head pointer as observed by
148 The head pointer is incremented by the controller as it takes commands off
149 of the submission queue.
150 .It Va dev.nvme.0.ioq0.sq_tail
151 (R) Current location of the submission queue tail pointer as observed by
153 The driver increments the tail pointer after writing a command
154 into the submission queue to signal that a new command is ready to be
156 .It Va dev.nvme.0.ioq0.cq_head
157 (R) Current location of the completion queue head pointer as observed by
159 The driver increments the head pointer after finishing
160 with a completion entry that was posted by the controller.
161 .It Va dev.nvme.0.ioq0.num_cmds
162 (R) Number of commands that have been submitted on this queue pair.
163 .It Va dev.nvme.0.ioq0.dump_debug
164 (W) Writing 1 to this sysctl will dump the full contents of the submission
165 and completion queues to the console.
176 driver first appeared in
182 driver was developed by Intel and originally written by
183 .An Jim Harris Aq Mt jimharris@FreeBSD.org ,
184 with contributions from
188 This man page was written by
189 .An Jim Harris Aq Mt jimharris@FreeBSD.org .