ext4dist(8) System Manager's Manual ext4dist(8)
NAME
ext4dist - Summarize ext4 operation latency. Uses Linux eBPF/bcc.
SYNOPSIS
ext4dist [-h] [-T] [-m] [-p PID] [interval] [count]
DESCRIPTION
This tool summarizes time (latency) spent in common ext4 file opera-
tions: reads, writes, opens, and syncs, and presents it as a power-of-2
histogram. It uses an in-kernel eBPF map to store the histogram for ef-
ficiency.
Since this works by tracing the ext4_file_operations interface func-
tions, 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 ext4 operation time, and print a summary on Ctrl-C:
# ext4dist
Trace PID 181 only:
# ext4dist -p 181
Print 1 second summaries, 10 times:
# ext4dist 1 10
1 second summaries, printed in milliseconds
# ext4dist -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 ext4 operations, in-
cluding 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.
https://github.com/iovisor/bcc
Also look in the bcc distribution for a companion _examples.txt file
containing example usage, output, and commentary for this tool.
OS
Linux
STABILITY
Unstable - in development.
AUTHOR
Brendan Gregg
SEE ALSO
ext4snoop(8)
USER COMMANDS 2016-02-12 ext4dist(8)
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