'\" t
.\"     Title: nvme-top
.\"    Author: [FIXME: author] [see http://www.docbook.org/tdg5/en/html/author]
.\" Generator: DocBook XSL Stylesheets vsnapshot <http://docbook.sf.net/>
.\"      Date: 10/30/2026
.\"    Manual: NVMe Manual
.\"    Source: NVMe
.\"  Language: English
.\"
.TH "NVME\-TOP" "1" "10/30/2026" "NVMe" "NVMe Manual"
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.SH "NAME"
nvme-top \- Show live I/O statistics of the NVMe subsystems
.SH "SYNOPSIS"
.sp
.nf
\fInvme\fR [<global\-options>] \fItop\fR [\-\-delay=<seconds> | \-d <seconds>]
.fi
.SH "DESCRIPTION"
.sp
Shows the subsystems with their I/O rates, refreshed every few seconds, like top(1)\&. Enter shows the namespaces, the paths and the controllers of a subsystem, with their rates, the retries and errors, the multipath failovers and the controller resets and reconnects\&.
.sp
With \fI\-\-output\-format=json\fR, takes two samples \fI\-\-delay\fR seconds apart, prints the rates and the counters as one JSON document, and exits\&. This is the output for scripts and monitoring tools\&.
.sp
The rates come from the block layer statistics of the namespaces and the paths\&. A rate is per second, a latency is the average time of an I/O in milliseconds, and the utilization is the share of the interval the device was busy\&. The rates of a subsystem and a controller are the sum of those of their namespaces or paths, the latency and the utilization the highest of them\&.
.SH "OPTIONS"
.PP
\-d <seconds>, \-\-delay=<seconds>
.RS 4
The time between two refreshes, or between the two samples of the JSON output\&. The default is 1\&.
.RE
.SH "GLOBAL OPTIONS"
.sp
The following options are defined at the top\-level nvme command and are available to this subcommand:
.PP
\-\-dry\-run
.RS 4
Print the command that would be executed, but do not actually execute it\&.
.RE
.PP
\-\-no\-ioctl\-probing
.RS 4
Disable probing for 64\-bit IOCTL support\&.
.RE
.PP
\-\-no\-retries
.RS 4
Disable retry logic on transient errors\&.
.RE
.PP
\-o <fmt>, \-\-output\-format=<fmt>
.RS 4
Set the reporting format to
\fInormal\fR,
\fItabular, \*(Aqjson\fR, or
\fIbinary\fR\&. Only one output format may be used at a time\&.
.RE
.PP
\-\-output\-format\-version=<version>
.RS 4
Select the output format version\&. Version
\fI1\fR
uses the original field naming, while version
\fI2\fR
(default) provides more consistent and script\-friendly field names\&. Other versions are rejected\&.
.RE
.PP
\-\-quiet
.RS 4
Suppress informational messages\&. Errors are still reported, and \-\-quiet cancels any \-\-verbose for the library log level\&.
.RE
.PP
\-\-set\-options=<key=value>[,<key=value>\&...]
.RS 4
Set libnvme library options for this invocation\&. Supported keys are
\fIforce\-4k\fR,
\fImi\-probe\-enabled\fR,
\fItest\-base\-dir\fR
and
\fItest\-sysfs\-dir\fR\&.
.RE
.PP
\-\-timeout=<ms>
.RS 4
Set the timeout for the command in milliseconds\&.
\fIinfinite\fR
or
\fI\-1\fR
waits without a time limit (0xffffffff)\&.
.RE
.PP
\-v, \-\-verbose
.RS 4
Increase the level of detail in the output\&. May be specified multiple times to further increase verbosity\&.
.RE
.sp
These options can also be set as machine\-wide defaults in nvme\-cli\&.conf(5)\&. A command\-line flag always overrides the file\&.
.SH "JSON OUTPUT"
.sp
The document has the \fIInterval\fR in seconds and a \fISubsystems\fR array\&. A subsystem has its \fIName\fR, \fINQN\fR, \fIHostNQN\fR, \fIIOPolicy\fR, \fIModel\fR, \fISerial\fR, \fIFirmware\fR and \fIType\fR, its \fIStats\fR, a \fINamespaces\fR array and a \fIControllers\fR array\&.
.sp
A namespace of a multipath subsystem has its \fIName\fR, \fINSID\fR, the \fIRequeueIO\fR and \fIFailIO\fR counts of the I/O which found no usable path, its \fIStats\fR and a \fIPaths\fR array\&. A path has its \fIName\fR, \fIController\fR, \fIANAState\fR, \fINUMANodes\fR, \fIQdepth\fR, the \fIRetries\fR, \fIFailovers\fR and \fIErrors\fR counts and its \fIStats\fR\&.
.sp
A namespace of a subsystem without multipath has its \fIName\fR, \fINSID\fR, \fIController\fR, the \fIRetries\fR and \fIErrors\fR counts and its \fIStats\fR\&.
.sp
A controller has its \fIName\fR, \fITransport\fR, \fIAddress\fR, \fIState\fR, \fINUMANode\fR, the number of \fIPaths\fR of a multipath subsystem, the \fIResets\fR, \fIReconnects\fR and \fIErrors\fR counts and its \fIStats\fR\&.
.sp
The \fIStats\fR of a namespace or a path are \fIReadIOPS\fR, \fIWriteIOPS\fR, \fIReadLatencyMs\fR, \fIWriteLatencyMs\fR, \fIReadBytesPerSec\fR, \fIWriteBytesPerSec\fR, \fIInflights\fR and \fIUtilPercent\fR\&. Those of a subsystem or a controller have \fIMaxReadLatencyMs\fR, \fIMaxWriteLatencyMs\fR and \fIMaxUtilPercent\fR instead of the latencies and the utilization, and no \fIInflights\fR\&.
.sp
A counter or an attribute the kernel does not provide is left out\&.
.SH "EXAMPLES"
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
Watch the subsystems, refreshed every 2 seconds:
.sp
.if n \{\
.RS 4
.\}
.nf
# nvme top \-\-delay=2
.fi
.if n \{\
.RE
.\}
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
Print the rates over 5 seconds as JSON:
.sp
.if n \{\
.RS 4
.\}
.nf
# nvme top \-\-delay=5 \-\-output\-format=json
.fi
.if n \{\
.RE
.\}
.RE
.SH "NVME"
.sp
Part of the nvme\-user suite