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nfsdist(8) | System Manager's Manual | nfsdist(8) |
NAME¶
nfsdist - Summarize NFS operation latency. Uses Linux eBPF/bcc.SYNOPSIS¶
nfsdist [-h] [-T] [-m] [-p PID] [interval] [count]DESCRIPTION¶
This tool summarizes time (latency) spent in common NFS file operations: reads, writes, opens, and getattrs, and presents it as a power-of-2 histogram. It uses an in-kernel eBPF map to store the histogram for efficiency.Since this works by tracing the nfs_file_operations interface functions, it will need updating to match any changes to these functions.
Since this uses BPF, only the root user can use this tool.
REQUIREMENTS¶
CONFIG_BPF and bcc.OPTIONS¶
- -h
- Print usage message.
- -T
- Don't include timestamps on interval output.
- -m
- Output in milliseconds.
- -p PID
- Trace this PID only.
EXAMPLES¶
- Trace NFS operation time, and print a summary on Ctrl-C:
- # nfsdist
- Trace PID 181 only:
- # nfsdist -p 181
- Print 1 second summaries, 10 times:
- # nfsdist 1 10
- 1 second summaries, printed in milliseconds
- # nfsdist -m 1
FIELDS¶
- msecs
- Range of milliseconds for this bucket.
- usecs
- Range of microseconds for this bucket.
- count
- Number of operations in this time range.
- distribution
- ASCII representation of the distribution (the count column).
OVERHEAD¶
This adds low-overhead instrumentation to these NFS operations, including reads and writes from the file system cache. Such reads and writes can be very frequent (depending on the workload; eg, 1M/sec), at which point the overhead of this tool may become noticeable. Measure and quantify before use.SOURCE¶
This is from bcc.Also look in the bcc distribution for a companion _examples.txt file containing example usage, output, and commentary for this tool.
OS¶
LinuxSTABILITY¶
Unstable - in development.AUTHOR¶
Samuel NairSEE ALSO¶
nfsslower(8)2017-09-08 | USER COMMANDS |