DOKK / manpages / debian 12 / bpfcc-tools / ext4dist-bpfcc.8.en
ext4dist(8) System Manager's Manual ext4dist(8)

ext4dist - Summarize ext4 operation latency. Uses Linux eBPF/bcc.

ext4dist [-h] [-T] [-m] [-p PID] [interval] [count]

This tool summarizes time (latency) spent in common ext4 file operations: 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 efficiency.

Since this works by tracing the ext4_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.

CONFIG_BPF and bcc.

Print usage message.
Don't include timestamps on interval output.
Output in milliseconds.
Trace this PID only.

# ext4dist
# ext4dist -p 181
# ext4dist 1 10
1 second summaries, printed in milliseconds
# ext4dist -m 1

Range of milliseconds for this bucket.
Range of microseconds for this bucket.
Number of operations in this time range.
ASCII representation of the distribution (the count column).

This adds low-overhead instrumentation to these ext4 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.

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.

Linux

Unstable - in development.

Brendan Gregg

ext4snoop(8)

2016-02-12 USER COMMANDS