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)