2 .\" Copyright (c) 2012-2013 Intel Corporation
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11 .\" 2. Redistributions in binary form must reproduce at minimum a disclaimer
12 .\" substantially similar to the "NO WARRANTY" disclaimer below
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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 surface NVM Express namespaces as disk devices.
58 Note that in NVM Express terms, a namespace is roughly equivalent to a
63 driver provides support for NVM Express (NVMe) controllers, such as:
66 Hardware initialization
68 Per-CPU IO queue pairs
70 API for registering NVMe namespace consumers such as
73 API for submitting NVM commands to namespaces
75 Ioctls for controller and namespace configuration and management
77 creates controller devices in the format /dev/nvmeX and namespace devices in
78 the format /dev/nvmeXnsY.
79 Note that the NVM Express specification starts numbering namespaces at 1,
80 not 0, and this driver follows that convention.
85 will create an I/O queue pair for each CPU, provided enough MSI-X vectors
87 To force a single I/O queue pair shared by all CPUs, set the following
90 .Bd -literal -offset indent
91 hw.nvme.per_cpu_io_queues=0
94 To force legacy interrupts for all
96 driver instances, set the following tunable value in
98 .Bd -literal -offset indent
102 Note that use of INTx implies disabling of per-CPU I/O queue pairs.
104 The following controller-level sysctls are currently implemented:
105 .Bl -tag -width indent
106 .It Va dev.nvme.0.int_coal_time
107 (R/W) Interrupt coalescing timer period in microseconds. Set to 0 to disable.
108 .It Va dev.nvme.0.int_coal_threshold
109 (R/W) Interrupt coalescing threshold in number of command completions.
113 The following queue pair-level sysctls are currently implemented.
114 Admin queue sysctls take the format of dev.nvme.0.adminq and I/O queue sysctls
115 take the format of dev.nvme.0.ioq0.
116 .Bl -tag -width indent
117 .It Va dev.nvme.0.ioq0.num_entries
118 (R) Number of entries in this queue pair's command and completion queue.
119 .It Va dev.nvme.0.ioq0.num_tr
120 (R) Number of nvme_tracker structures currently allocated for this queue pair.
121 .It Va dev.nvme.0.ioq0.num_prp_list
122 (R) Number of nvme_prp_list structures currently allocated for this queue pair.
123 .It Va dev.nvme.0.ioq0.sq_head
124 (R) Current location of the submission queue head pointer as observed by
126 The head pointer is incremented by the controller as it takes commands off
127 of the submission queue.
128 .It Va dev.nvme.0.ioq0.sq_tail
129 (R) Current location of the submission queue tail pointer as observed by
131 The driver increments the tail pointer after writing a command
132 into the submission queue to signal that a new command is ready to be
134 .It Va dev.nvme.0.ioq0.cq_head
135 (R) Current location of the completion queue head pointer as observed by
137 The driver increments the head pointer after finishing
138 with a completion entry that was posted by the controller.
139 .It Va dev.nvme.0.ioq0.num_cmds
140 (R) Number of commands that have been submitted on this queue pair.
141 .It Va dev.nvme.0.ioq0.dump_debug
142 (W) Writing 1 to this sysctl will dump the full contents of the submission
143 and completion queues to the console.
153 driver first appeared in
159 driver was developed by Intel and originally written by
160 .An Jim Harris Aq jimharris@FreeBSD.org ,
161 with contributions from Joe Golio at EMC.
163 This man page was written by
164 .An Jim Harris Aq jimharris@FreeBSD.org .