Section 8 · System administration

bcc-drsnoop.8

Package: bcc-tools

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drsnoop

NAME
SYNOPSIS
DESCRIPTION
REQUIREMENTS
OPTIONS
EXAMPLES
FIELDS
OVERHEAD
SOURCE
OS
STABILITY
AUTHOR

NAME

drsnoop − Trace direct reclaim events. Uses Linux eBPF/bcc.

SYNOPSIS

drsnoop [−h] [−T] [−U] [−p PID] [−t TID] [−u UID] [−d DURATION] [-n name] [-v]

DESCRIPTION

drsnoop trace direct reclaim events, showing which processes are allocing pages with direct reclaiming. This can be useful for discovering when allocstall (/p- roc/vmstat) continues to increase, whether it is caused by some critical proc- esses or not.

This works by tracing the direct reclaim events using kernel tracepoints.

This makes use of a Linux 4.4 feature (bpf_perf_event_output()); for kernels older than 4.4, see the version under tools/old, which uses an older mechanism.

Since this uses BPF, only the root user can use this tool.

REQUIREMENTS

CONFIG_BPF and bcc.

OPTIONS


	−h		Print usage message.
	−T		Include a timestamp column.
	−U		Show UID.
	−p PID		Trace this process ID only (filtered in-kernel).
	−t TID		Trace this thread ID only (filtered in-kernel).
	−u UID		Trace this UID only (filtered in-kernel).

−d DURATION

Total duration of trace in seconds.

−n name

Only print processes where its name partially matches ’name’ −v verbose Run in verbose mode. Will output system memory state


	−v		show system memory state

EXAMPLES

Trace all direct reclaim events:

drsnoop

Trace all direct reclaim events, for 10 seconds only:

drsnoop -d 10

Trace all direct reclaim events, and include timestamps:

drsnoop −T

Show UID:

drsnoop −U

Trace PID 181 only:

drsnoop −p 181

Trace UID 1000 only:

drsnoop −u 1000

Trace all direct reclaim events from processes where its name partially
match-

es ’mond’: # drnsnoop −n mond

FIELDS

TIME(s)

Time of the call, in seconds.


	UID		User ID
	PID		Process ID
	TID		Thread ID
	COMM		Process name

OVERHEAD

This traces the kernel direct reclaim tracepoints and prints output for each event. As the rate of this is generally expected to be low (< 1000/s), the overhead is also expected to be negligible.

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

Wenbo Zhang