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Instruments User Guide

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I/O Activity Instrument

Overview

Instrument Description

The I/O Activity instrument captures information about I/O events.

Supported Platforms

iOS

Related Profiling Templates

System Usage Profiling Template

Timeline Pane

The timeline pane displays the following information, based on the instrument’s configuration:

Display name

Definition

Sample Number (#)

The sequence number of the event.

Duration

The duration of the function call in microseconds.

In File (infiledes)

The input file descriptor.

In Bytes (inbytes)

The requested number of bytes to read or write.

Out File (outfiledes)

The output file descriptor.

Out Bytes (outbytes)

The actual number of bytes read or written.

Thread ID (tid)

The thread identifier.

Stack Depth

The number of stack frames in use during this function call.

Record Settings

Click the Record Settings button (image: ../Art/instruments_recordsettings_button_inline_2x.png) in the inspector pane to customize the following recording options.

Sampling Rate

Set how often the instrument records information. The slider allows sampling from 1/10th of a second to 1 second in 1/10 of a second increments. The text field allows for other 1/10th increments. The default value is 1/10th of a second.

System Statistics

Select a statistic to see it graphed in the timeline pane. Click the shape or the color well to change how a statistic is represented.

Select statistics to list

Select the statistics to be displayed in the System Statistics area.

Display Settings

Click the Display Settings button (image: ../Art/instruments_displaysettings_button_inline_2x.png) in the inspector pane to customize the following display settings.

Track Display Settings

These settings control how information is displayed in the timeline pane.

Setting

Description

Options

Style

How information is presented.

  • Block Graph: Information is presented as a horizontal line until the information changes. The area under the line is filled by the statistic’s designated color.

Active Probes

The following active probes display settings are available.

Setting

Bundled probes

State

File Attributes

getattrlist

setattrlist

listxattr

On by default.

File Permissions

chmod

fchmod

chown

fchown

lchown

access

On by default.

Open and Close

open

fdopen

fopen

freopen

close

fclose

On by default.

Other

lseek

fsync

dup

dup2

link

unlink

Off by default.

Read and Write

read

pread

readv

write

pwrite

writev

On by default.

Shared Memory

shm_open

shm_unlink

Off by default.

Sockets

recv

recvfrom

recvmsg

send

sendmsg

sendto

Off by default.

Stats

lstat

lstat64

stat

stat64

fstat

fstat64

Off by default.

Call Tree

The following call tree display settings filter the call tree in the detail pane.

Setting

State

Separate by Thread

Off by default.

Invert Call Tree

On by default.

Hide System Libraries

Off by default.

Flatten Recursion

Off by default.

Call Tree Constraints

The following options filter the call tree to display calls that fall within a specific threshold based on the settings below.

Setting

State

# Calls

Off by default.

Data Mining

Allows you to filter through the collected data for specific symbols and libraries.

Detail Pane Columns

Summary Detail Type

The following summary columns are available in the detail pane.

Column name

Definition

#

The sequence number.

Function

The name of the function being called.

Duration µs

The duration of the function call in microseconds.

In File

The input file descriptor.

In Bytes

The requested number of bytes to read or write.

Out File

The output file descriptor.

Out Bytes

The actual number of bytes read or written.

Thread ID

The thread identifier.

Stack Depth

The number of stack frames in use during this function call.

Error

The most recent error during the function call.

Path

The path to the file on which the executable performed the operation.

Parameters

The parameters for the function call. See the API for the specific function for more details.

Call Tree Detail Type

The following call tree columns are available in the detail pane.

Column name

Definition

Self %

The percentage of time the symbol references itself.

Total %

The total percentage of time that the symbol is used.

Library

The name of the library that generated the call.

Category

An icon representing the category of the call.

Symbol Name

The name of the symbol being called.