Macos Memory

macOS Memory Analysis Skill

Comprehensive guide for analyzing memory usage and detecting leaks in native macOS applications using Apple's native profiling tools.

1. leaks - Memory Leak Detection

The leaks tool detects unreachable memory allocations that have been leaked.

Basic Usage

leaks <pid>

Check a running process for memory leaks:

leaks 1234

Run App and Check at Exit

Run an application and automatically check for leaks when it exits:

leaks --atExit -- ./myapp
leaks --atExit -- /path/to/binary arg1 arg2

Common Options

• leaks <pid> - Check running process
• leaks --atExit -- <command> - Check application at exit
• leaks --nocontext - Suppress stack trace context
• leaks --nostacks - Don't print stack traces (faster)

Example Output

The tool will report:

• Number of leaked memory blocks
• Total leaked memory size
• Stack traces showing where leaks originated

2. heap - Heap Analysis

The heap tool provides detailed information about heap memory allocations.

Basic Usage

heap <pid>

Show heap summary:

heap 1234

Show All Allocations

heap <pid> -addresses all

Dump all allocation addresses (detailed, slow for large heaps):

heap 1234 -addresses all

Common Options

• heap <pid> - Show heap summary
• heap <pid> -addresses all - Show all individual allocations
• heap <pid> -addresses <size> - Show allocations above a certain size
• heap <pid> -diffFrom <file> - Compare heap to a previous snapshot

Interpretation

• Zone - Memory zone information
• Count - Number of allocations
• Total - Total allocated bytes
• Avg - Average allocation size
• Max - Largest single allocation

3. vmmap - Virtual Memory Map

The vmmap tool shows the complete virtual memory map of a process, including all memory regions and their usage.

Basic Usage

vmmap <pid>

Show full virtual memory map:

vmmap 1234

Filter for Malloc Regions

vmmap <pid> | grep MALLOC

Memory Region Types

Common memory region types in output:

• MALLOC - Memory allocated by malloc
• STACK - Thread stacks
• TEXT - Code/executable sections
• DATA - Static data
• PAGEZERO - Zero page (guard region)
• OBJC - Objective-C runtime
• CF - CoreFoundation

Example Analysis

vmmap 1234 | grep -E "MALLOC|TOTAL"

Shows only malloc regions and totals for quick overview.

4. Instruments CLI - Advanced Profiling

The xcrun instruments command-line tool provides professional profiling capabilities.

Leaks Instrument

Detect memory leaks while capturing detailed information:

xcrun instruments -t "Leaks" ./myapp
xcrun instruments -t "Leaks" -l 30000 ./myapp

Allocations Instrument

Track all memory allocations:

xcrun instruments -t "Allocations" ./myapp
xcrun instruments -t "Allocations" -l 30000 ./myapp

Common Options

• -t "Name" - Instrument template to use
• -l <duration> - Recording duration in milliseconds
• -o <path> - Output file path (.trace format)
• -s <delay> - Start delay in milliseconds
• -p <PID> - Attach to running process

Available Instruments

Common instruments for memory analysis:

• Leaks - Memory leak detection
• Allocations - Memory allocation tracking
• VM Tracker - Virtual memory analysis
• System Trace - Low-level system events

Saving Results

xcrun instruments -t "Leaks" -o /tmp/myapp.trace ./myapp

Results can be opened in Instruments.app for GUI analysis.

5. Finding Process ID (PID)

Using pgrep

Find process by partial name match:

pgrep -f kattle
pgrep -f "kattle.*--flag"

Get first matching PID:

pgrep -f kattle | head -1

Using ps

Alternative method with ps:

ps aux | grep kattle
ps aux | grep -i "MyApp"

Extract PID from ps output:

ps aux | grep kattle | grep -v grep | awk '{print $2}'

Using Activity Monitor CLI

open -a Activity\ Monitor

Workflow Examples

Quick Memory Check

PID=$(pgrep -f kattle | head -1)
echo "Process: kattle (PID: $PID)"
ps -o rss= -p $PID | awk '{printf "RSS: %.2f MB\n", $1/1024}'

Comprehensive Leak Detection

PID=$(pgrep -f myapp | head -1)
echo "=== Leak Detection ==="
leaks $PID

echo "=== Heap Summary ==="
heap $PID

echo "=== Top Malloc Regions ==="
vmmap $PID | grep -i malloc | head -10

Profile Until Problem Occurs

# Start profiling with Leaks instrument
xcrun instruments -t "Leaks" -o /tmp/profile.trace ./myapp

# Open results in Instruments.app
open /tmp/profile.trace

Memory Growth Analysis

PID=$(pgrep -f myapp | head -1)

# Capture initial heap snapshot
heap $PID > /tmp/heap_initial.txt

# Wait for activity
sleep 10

# Compare with second snapshot
heap $PID -diffFrom /tmp/heap_initial.txt

Tips and Best Practices

1. Run as appropriate user - May need sudo for privileged processes
2. Stop background activity - Close other apps to reduce noise
3. Warm up the app - Run app briefly to reach stable state
4. Use vmmap for overview - Get big picture of memory usage
5. Use heap for detail - Drill down into allocation patterns
6. Use leaks for confirmation - Verify suspected leaks
7. Capture baselines - Take snapshots at known good states
8. Compare snapshots - Use diff features to find growth

Common Issues

Tool Not Found

If tools aren't in PATH, use full paths:

/usr/bin/leaks <pid>
/usr/bin/heap <pid>
/usr/bin/vmmap <pid>

Permission Denied

Need appropriate privileges for some processes:

sudo leaks <pid>
sudo xcrun instruments -t "Leaks" ./app

Instruments Framework Issues

Ensure Xcode command line tools are installed:

xcode-select --install

Related Commands

• sample - CPU profiling sampler
• dtrace - Dynamic tracing
• malloc_history - Track malloc allocations
• memory_statistics - System-wide memory stats

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