Sample Process

Select the process, then click the More button (the three dots) at the top of the window and choose Sample Process. You can also double-click the process and click Sample in the window that opens.

When the report appears, you can save it as a text file and attach it to a bug report or support request.

Run sample <PID> 5 to sample a process for 5 seconds. You can use part of the process name instead of the PID. The report is printed and saved to a file, and the path is shown when it finishes.

The report starts with a header: the process name and PID, its path, its parent process, the code type, and the macOS version. The part that matters comes next, under Call graph.

The call graph lists each thread. The main thread, the one that handles clicks and key presses, is labeled com.apple.main-thread. Under each thread, functions are indented to show which function called which. The number at the start of a line is how many times that function was on the stack when a sample was taken.

• Follow the lines with the largest numbers down to the deepest indent. That is where the thread spent most of its time.
• If the deepest lines on the main thread are waiting calls such as mach_msg, __psynch_cvwait or __semwait_signal, the thread was blocked waiting on something else.
• If the deepest lines are the app's own functions with large counts, the thread was busy doing work.
• The "Sort by top of stack" section near the end lists the functions that were running most often, which is a quick summary of the same data.
• The Binary Images list at the end names the frameworks and libraries loaded in the process.

The sample command gives you more control than Activity Monitor. Its default length is 10 seconds, and you can change it.

1. Open Terminal from Applications > Utilities.
2. Find the process ID with pgrep -lx Safari, replacing Safari with the process name.
3. Run sample <PID> 10 -file ~/Desktop/sample.txt while the problem is happening.
4. Open the file on your Desktop, or attach it to a bug report.

A sample is a snapshot of one process. Use it when you already know which app is the problem.

• Helpful: an app is frozen, one process keeps a high % CPU, or an app is slow at a specific task you can repeat.
• Less helpful: the whole Mac is slow and you do not know why. A spindump, which covers every process, fits that better.
• Not helpful: the problem has already passed. A sample only shows what happened while it ran.

A sample on its own is useful, but a short note makes it much easier to act on.

1. Take the sample while the app is frozen or busy, not after it recovers.
2. Save the report as a text file instead of copying part of it. Developers need the whole call graph and the Binary Images list.
3. Write down what you were doing when the problem started, such as the file you opened or the button you clicked.
4. Include the app's version and your macOS version. Both also appear in the report header, next to Version and OS Version.
5. Send it through the app's support page or bug tracker, or to Apple through Feedback Assistant if the app is from Apple.