Manual: ext4dist-bpfcc

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 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.

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, 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  over‐
       head 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)