# mem_monitor

**Repository Path**: DDL/mem_monitor

## Basic Information

- **Project Name**: mem_monitor
- **Description**: Monitor memory leak and peak memory snapshot by LD_PRELOAD.
- **Primary Language**: Unknown
- **License**: Not specified
- **Default Branch**: master
- **Homepage**: None
- **GVP Project**: No

## Statistics

- **Stars**: 0
- **Forks**: 0
- **Created**: 2026-01-18
- **Last Updated**: 2026-01-18

## Categories & Tags

**Categories**: Uncategorized

**Tags**: None

## README

# mem_monitor

mem_monitor is an Android bionic LD_PRELOAD memory/FD leak monitor built for the Soong build system.
It tracks malloc/mmap/dmabuf/ION and file descriptor leaks, captures peak memory snapshots, and
exports per-process reports in txt and html formats. A separate aggregator tool merges per-process
reports into a single summary.

## Features

- Android bionic compatible LD_PRELOAD library
- Track malloc/calloc/realloc/memalign allocations
- Track mmap/munmap allocations (optionally file-backed)
- Track file descriptor open/close leaks
- Track DMA-BUF allocations via dma-heap ioctl
- Track ION allocations via ion ioctl
- Peak memory snapshot aggregation by call stack
- Periodic report flush without signal-based sampling
- Per-process report files + multi-process aggregated report
- Configurable stack depth and top-N snapshot entries

## Build (Soong)

Copy this project into your AOSP tree and build:

```
mmm path/to/mem_monitor
```

Outputs:
- `libmemmon_preload.so`
- `memmon_report_aggregator`

## Deploy

Push artifacts to the device:

```
adb push out/target/product/<product>/system/lib64/libmemmon_preload.so /data/local/tmp/
adb push out/target/product/<product>/system/bin/memmon_report_aggregator /data/local/tmp/
```

(Use lib for 32-bit processes.)

## Usage

### 1) LD_PRELOAD for a target process

For a debuggable app:

```
adb shell setprop wrap.<package> "LD_PRELOAD=/data/local/tmp/libmemmon_preload.so"
adb shell am force-stop <package>
adb shell am start -n <package>/<activity>
```

For native services (init rc), add:

```
setenv LD_PRELOAD /data/local/tmp/libmemmon_preload.so
```

### 2) Configure tracking

Use env vars or a config file.

Env vars:

- `MEMMON_TRACK`: comma list of `malloc,mmap,fd,dmabuf,ion`
- `MEMMON_STACK_DEPTH`: call stack depth (default 16)
- `MEMMON_REPORT_DIR`: report output directory
- `MEMMON_SNAPSHOT_INTERVAL_MS`: periodic flush interval (0 disables)
- `MEMMON_PEAK_TOP_N`: top snapshot entries
- `MEMMON_MIN_ALLOC`: ignore allocations smaller than this size
- `MEMMON_CONFIG`: path to config file

Config file example:

```
# /data/local/tmp/memmon.cfg
track=malloc,mmap,fd,dmabuf,ion
stack_depth=24
report_dir=/data/local/tmp/memmon
snapshot_interval_ms=10000
peak_top_n=64
min_alloc=128
```

### 3) Collect reports

Per-process reports will be created under `MEMMON_REPORT_DIR`:

- `<process>_<timestamp>.txt`
- `<process>_<timestamp>.html`

### 4) Aggregate multi-process reports

```
adb shell /data/local/tmp/memmon_report_aggregator --input-dir /data/local/tmp/memmon --output-prefix memmon_summary
```

Output:

- `/data/local/tmp/memmon/memmon_summary.txt`
- `/data/local/tmp/memmon/memmon_summary.html`

## Report contents

Each per-process report includes:

- Process name
- Current bytes and peak bytes
- Peak snapshot time
- Top-N aggregated snapshot entries with call stacks
- Leak allocations with call stacks
- Leak file descriptors with call stacks

## ION/DMA-BUF tracking notes

- dma-heap allocations are tracked via `DMA_HEAP_IOCTL_ALLOC`.
- ION allocations are tracked via `ION_IOC_ALLOC`.
- The report associates these allocations with the calling stack.

Some vendor ION variants or custom allocators may require extending the ioctl parsing.

## Safety and stability

- The sampling path does not use signals to avoid killing the target process.
- Reports are flushed periodically when `MEMMON_SNAPSHOT_INTERVAL_MS` is set.
- Reports are also flushed at process exit.

## Extension ideas

- Add JSON report format for automation
- Export to `perfetto` or `trace_marker` for timeline correlation
- Track `ashmem` and `memfd` allocations
- Add per-allocator sampling mode to reduce overhead
- Add symbolization using `unwindstack` for richer stacks

## Notes

- LD_PRELOAD requires debuggable apps or appropriate system configuration.
- Running as root may be required for system services.
- This library is intended for debugging and should not be enabled in production builds.