NAME

       btrfsdist - Summarize btrfs operation latency. Uses Linux eBPF/bcc.

SYNOPSIS

       btrfsdist [-h] [-T] [-N] [-d] [interval] [count]

DESCRIPTION

       This  tool  summarizes  time  (latency)  spent in common btrfs 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 btrfs_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 btrfs operation time, and print a summary on Ctrl-C:
              # btrfsdist

       Trace PID 181 only:
              # btrfsdist -p 181

       Print 1 second summaries, 10 times:
              # btrfsdist 1 10

       1 second summaries, printed in milliseconds
              # btrfsdist -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 btrfs writes and fsyncs, as well as all system reads and  opens
       (due  to  the current implementation of the btrfs_file_operations interface). Particularly, all reads and
       writes from the file system cache will incur extra overhead while tracing. 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

       btrfsslower(8)