Using system tracing tools like perf
and ftrace
in Linux can help you gain insights into the performance and behavior of your system. Here's how you can use each of these tools:
Using Perf:
perf
is installed on your system. On most Linux distributions, it can be installed using the package manager, such as sudo apt-get install linux-perf
on Ubuntu.Basic Usage: To start recording events, you can use the perf record
command. For instance, to record CPU cycles, you would use:
<code>sudo perf record -e cycles -a sleep 10</code>
This command records CPU cycles for all CPUs for 10 seconds.
Analysis: After recording, you can analyze the data with perf report
:
<code>sudo perf report</code>
This command will open an interactive interface where you can navigate through the data.
Specific Use Cases: Perf can be used to profile specific applications, analyze system-wide performance, and more. For example, to profile a specific application:
<code>sudo perf record ./my_application sudo perf report</code>
Using Ftrace:
Enabling Ftrace: Ftrace is typically part of the Linux kernel. To enable it, you need to mount the debug filesystem:
<code>sudo mount -t debugfs nodev /sys/kernel/debug</code>
Configuring Ftrace: You can configure what to trace by writing to files in /sys/kernel/debug/tracing
. For example, to trace function calls:
<code>echo function > /sys/kernel/debug/tracing/current_tracer echo 1 > /sys/kernel/debug/tracing/tracing_on</code>
Viewing Output: The trace output can be viewed in real-time using:
<code>cat /sys/kernel/debug/tracing/trace</code>
Stopping the Trace: To stop tracing, write 0
to the tracing_on
file:
<code>echo 0 > /sys/kernel/debug/tracing/tracing_on</code>
Key Differences:
Functionality:
Perf
is a more versatile tool that can trace a wide variety of events, including hardware events (e.g., CPU cycles, cache misses) and software events (e.g., page faults, context switches).Ftrace
is specifically designed to trace kernel functions and system calls, providing detailed kernel-level tracing.User Interface:
Perf
offers an interactive interface (perf report
) for analyzing recorded data, which can be very user-friendly.Ftrace
provides raw output that requires manual parsing or scripting to analyze effectively.Overhead:
Perf
generally has higher overhead than ftrace
because of its broader capabilities.Ftrace
is lighter and can be used with minimal system impact, making it ideal for scenarios where low overhead is crucial.When to Use Each Tool:
Use Perf:
Use Ftrace:
Analyzing Perf Output:
perf report
: As mentioned, perf report
provides an interactive way to view recorded data. You can navigate through the call graph to identify functions that consume the most time or resources.perf
to analyze hardware events like CPU cycles, cache misses, and branch mispredictions. High counts in these areas can suggest optimization opportunities.Perf
uses statistical sampling to gather data, which can help identify hotspots in your code or system.Analyzing Ftrace Output:
trace-cmd
or write scripts to filter and parse the data.Common Pitfalls:
ftrace
.Best Practices:
perf
and ftrace
allow you to filter events. Use this feature to focus on the areas of interest and reduce data overload.perf
and ftrace
to get a more comprehensive view of system behavior.trace-cmd
for ftrace
or custom scripts for perf
can streamline your workflow.By following these guidelines, you can effectively use perf
and ftrace
to diagnose and optimize the performance of your Linux system.
The above is the detailed content of How do I use system tracing tools like perf and ftrace in Linux?. For more information, please follow other related articles on the PHP Chinese website!