# Native heap profiler NOTE: **heapprofd requires Android 10 or higher** Heapprofd is a tool that tracks native heap allocations & deallocations of an Android process within a given time period. The resulting profile can be used to attribute memory usage to particular call-stacks, supporting a mix of both native and java code. The tool can be used by Android platform and app developers to investigate memory issues. On debug Android builds, you can profile all apps and most system services. On "user" builds, you can only use it on apps with the debuggable or profileable manifest flag. ## Quickstart See the [Memory Guide](/docs/case-studies/memory.md#heapprofd) for getting started with heapprofd. ## UI Dumps from heapprofd are shown as flamegraphs in the UI after clicking on the diamond. Each diamond corresponds to a snapshot of the allocations and callstacks collected at that point in time.   ## SQL Information about callstacks is written to the following tables: * [`stack_profile_mapping`](/docs/analysis/sql-tables.autogen#stack_profile_mapping) * [`stack_profile_frame`](/docs/analysis/sql-tables.autogen#stack_profile_frame) * [`stack_profile_callsite`](/docs/analysis/sql-tables.autogen#stack_profile_callsite) The allocations themselves are written to [`heap_profile_allocation`](/docs/analysis/sql-tables.autogen#heap_profile_allocation). Offline symbolization data is stored in [`stack_profile_symbol`](/docs/analysis/sql-tables.autogen#stack_profile_symbol). See [Example Queries](#heapprofd-example-queries) for example SQL queries. ## Recording Heapprofd can be configured and started in three ways. #### Manual configuration This requires manually setting the [HeapprofdConfig](/docs/reference/trace-config-proto.autogen#HeapprofdConfig) section of the trace config. The only benefit of doing so is that in this way heap profiling can be enabled alongside any other tracing data sources. #### Using the tools/heap_profile script (recommended) You can use the `tools/heap_profile` script. If you are having trouble make sure you are using the [latest version]( https://raw.githubusercontent.com/google/perfetto/master/tools/heap_profile). You can target processes either by name (`-n com.example.myapp`) or by PID (`-p 1234`). In the first case, the heap profile will be initiated on both on already-running processes that match the package name and new processes launched after the profiling session is started. For the full arguments list see the [heap_profile cmdline reference page](/docs/reference/heap_profile-cli). #### Using the Recording page of Perfetto UI You can also use the [Perfetto UI](https://ui.perfetto.dev/#!/record/memory) to record heapprofd profiles. Tick "Heap profiling" in the trace configuration, enter the processes you want to target, click "Add Device" to pair your phone, and record profiles straight from your browser. This is also possible on Windows. ## Viewing the data The resulting profile proto contains four views on the data * **space**: how many bytes were allocated but not freed at this callstack the moment the dump was created. * **alloc\_space**: how many bytes were allocated (including ones freed at the moment of the dump) at this callstack * **objects**: how many allocations without matching frees were done at this callstack. * **alloc\_objects**: how many allocations (including ones with matching frees) were done at this callstack. _(Googlers: You can also open the gzipped protos using http://pprof/)_ TIP: you might want to put `libart.so` as a "Hide regex" when profiling apps. You can use the [Perfetto UI](https://ui.perfetto.dev) to visualize heap dumps. Upload the `raw-trace` file in your output directory. You will see all heap dumps as diamonds on the timeline, click any of them to get a flamegraph. Alternatively [Speedscope](https://speedscope.app) can be used to visualize the gzipped protos, but will only show the space view. TIP: Click Left Heavy on the top left for a good visualization. ## Sampling interval Heapprofd samples heap allocations by hooking calls to malloc/free and C++'s operator new/delete. Given a sampling interval of n bytes, one allocation is sampled, on average, every n bytes allocated. This allows to reduce the performance impact on the target process. The default sampling rate is 4096 bytes. The easiest way to reason about this is to imagine the memory allocations as a stream of one byte allocations. From this stream, every byte has a 1/n probability of being selected as a sample, and the corresponding callstack gets attributed the complete n bytes. For more accuracy, allocations larger than the sampling interval bypass the sampling logic and are recorded with their true size. See the [heapprofd Sampling](/docs/design-docs/heapprofd-sampling) document for details. ## Startup profiling When specifying a target process name (as opposite to the PID), new processes matching that name are profiled from their startup. The resulting profile will contain all allocations done between the start of the process and the end of the profiling session. On Android, Java apps are usually not exec()-ed from scratch, but fork()-ed from the [zygote], which then specializes into the desired app. If the app's name matches a name specified in the profiling session, profiling will be enabled as part of the zygote specialization. The resulting profile contains all allocations done between that point in zygote specialization and the end of the profiling session. Some allocations done early in the specialization process are not accounted for. At the trace proto level, the resulting [ProfilePacket] will have the `from_startup` field set to true in the corresponding `ProcessHeapSamples` message. This is not surfaced in the converted pprof compatible proto. [ProfilePacket]: /docs/reference/trace-packet-proto.autogen#ProfilePacket [zygote]: https://developer.android.com/topic/performance/memory-overview#SharingRAM ## Runtime profiling When a profiling session is started, all matching processes (by name or PID) are enumerated and are signalled to request profiling. Profiling isn't actually enabled until a few hundred milliseconds after the next allocation that is done by the application. If the application is idle when profiling is requested, and then does a burst of allocations, these may be missed. The resulting profile will contain all allocations done between when profiling is enabled, and the end of the profiling session. The resulting [ProfilePacket] will have `from_startup` set to false in the corresponding `ProcessHeapSamples` message. This does not get surfaced in the converted pprof compatible proto. ## Concurrent profiling sessions If multiple sessions name the same target process (either by name or PID), only the first relevant session will profile the process. The other sessions will report that the process had already been profiled when converting to the pprof compatible proto. If you see this message but do not expect any other sessions, run ```shell adb shell killall perfetto ``` to stop any concurrent sessions that may be running. The resulting [ProfilePacket] will have `rejected_concurrent` set to true in otherwise empty corresponding `ProcessHeapSamples` message. This does not get surfaced in the converted pprof compatible proto. ## {#heapprofd-targets} Target processes Depending on the build of Android that heapprofd is run on, some processes are not be eligible to be profiled. On _user_ (i.e. production, non-rootable) builds, only Java applications with either the profileable or the debuggable manifest flag set can be profiled. Profiling requests for non-profileable/debuggable processes will result in an empty profile. On userdebug builds, all processes except for a small set of critical services can be profiled (to find the set of disallowed targets, look for `never_profile_heap` in [heapprofd.te]( https://cs.android.com/android/platform/superproject/+/master:system/sepolicy/private/heapprofd.te?q=never_profile_heap). This restriction can be lifted by disabling SELinux by running `adb shell su root setenforce 0` or by passing `--disable-selinux` to the `heap_profile` script. | | userdebug setenforce 0 | userdebug | user | |-------------------------|:----------------------:|:---------:|:----:| | critical native service | Y | N | N | | native service | Y | Y | N | | app | Y | Y | N | | profileable app | Y | Y | Y | | debuggable app | Y | Y | Y | To mark an app as profileable, put `` into the `` section of the app manifest. ```xml ... ``` ## DEDUPED frames If the name of a Java method includes `[DEDUPED]`, this means that multiple methods share the same code. ART only stores the name of a single one in its metadata, which is displayed here. This is not necessarily the one that was called. ## Triggering heap snapshots on demand Heap snapshot are recorded into the trace either at regular time intervals, if using the `continuous_dump_config` field, or at the end of the session. You can also trigger a snapshot of all currently profiled processes by running `adb shell killall -USR1 heapprofd`. This can be useful in lab tests for recording the current memory usage of the target in a specific state. This dump will show up in addition to the dump at the end of the profile that is always produced. You can create multiple of these dumps, and they will be enumerated in the output directory. ## Symbolization ### Set up llvm-symbolizer You only need to do this once. To use symbolization, your system must have llvm-symbolizer installed and accessible from `$PATH` as `llvm-symbolizer`. On Debian, you can install it using `sudo apt install llvm-9`. This will create `/usr/bin/llvm-symbolizer-9`. Symlink that to somewhere in your `$PATH` as `llvm-symbolizer`. For instance, `ln -s /usr/bin/llvm-symbolizer-9 ~/bin/llvm-symbolizer`, and add `~/bin` to your path (or run the commands below with `PATH=~/bin:$PATH` prefixed). ### Symbolize your profile If the profiled binary or libraries do not have symbol names, you can symbolize profiles offline. Even if they do, you might want to symbolize in order to get inlined function and line number information. All tools (traceconv, trace_processor_shell, the heap_profile script) support specifying the `PERFETTO_BINARY_PATH` as an environment variable. ``` PERFETTO_BINARY_PATH=somedir tools/heap_profile --name ${NAME} ``` You can persist symbols for a trace by running `PERFETTO_BINARY_PATH=somedir tools/traceconv symbolize raw-trace > symbols`. You can then concatenate the symbols to the trace ( `cat raw-trace symbols > symbolized-trace`) and the symbols will part of `symbolized-trace`. The `tools/heap_profile` script will also generate this file in your output directory, if `PERFETTO_BINARY_PATH` is used. The symbol file is the first with matching Build ID in the following order: 1. absolute path of library file relative to binary path. 2. absolute path of library file relative to binary path, but with base.apk! removed from filename. 3. basename of library file relative to binary path. 4. basename of library file relative to binary path, but with base.apk! removed from filename. 5. in the subdirectory .build-id: the first two hex digits of the build-id as subdirectory, then the rest of the hex digits, with ".debug" appended. See https://fedoraproject.org/wiki/RolandMcGrath/BuildID#Find_files_by_build_ID For example, "/system/lib/base.apk!foo.so" with build id abcd1234, is looked for at: 1. $PERFETTO_BINARY_PATH/system/lib/base.apk!foo.so 2. $PERFETTO_BINARY_PATH/system/lib/foo.so 3. $PERFETTO_BINARY_PATH/base.apk!foo.so 4. $PERFETTO_BINARY_PATH/foo.so 5. $PERFETTO_BINARY_PATH/.build-id/ab/cd1234.debug Alternatively, you can set the `PERFETTO_SYMBOLIZER_MODE` environment variable to `index`, and the symbolizer will recursively search the given directory for an ELF file with the given build id. This way, you will not have to worry about correct filenames. ## Deobfuscation If your profile contains obfuscated Java methods (like `fsd.a`), you can provide a deobfuscation map to turn them back into human readable. To do so, use the `PERFETTO_PROGUARD_MAP` environment variable, using the format `packagename=filename[:packagename=filename...]`, e.g. `PERFETTO_PROGUARD_MAP=com.example.pkg1=foo.txt:com.example.pkg2=bar.txt`. All tools (traceconv, trace_processor_shell, the heap_profile script) support specifying the `PERFETTO_PROGUARD_MAP` as an environment variable. You can get a deobfuscation map for your trace using `tools/traceconv deobfuscate`. Then concatenate the resulting file to your trace to get a deobfuscated version of it. ``` PERFETTO_PROGUARD_MAP=com.example.pkg tools/traceconv deobfuscate ${TRACE} > deobfuscation_map cat ${TRACE} deobfuscation_map > deobfuscated_trace ``` ## Troubleshooting ### Buffer overrun If the rate of allocations is too high for heapprofd to keep up, the profiling session will end early due to a buffer overrun. If the buffer overrun is caused by a transient spike in allocations, increasing the shared memory buffer size (passing `--shmem-size` to `tools/heap_profile`) can resolve the issue. Otherwise the sampling interval can be increased (at the expense of lower accuracy in the resulting profile) by passing `--interval=16000` or higher. ### Profile is empty Check whether your target process is eligible to be profiled by consulting [Target processes](#heapprofd-targets) above. Also check the [Known Issues](#known-issues). ### Implausible callstacks If you see a callstack that seems to impossible from looking at the code, make sure no [DEDUPED frames](#deduped-frames) are involved. Also, if your code is linked using _Identical Code Folding_ (ICF), i.e. passing `-Wl,--icf=...` to the linker, most trivial functions, often constructors and destructors, can be aliased to binary-equivalent operators of completely unrelated classes. ### Symbolization: Could not find library When symbolizing a profile, you might come across messages like this: ```bash Could not find /data/app/invalid.app-wFgo3GRaod02wSvPZQ==/lib/arm64/somelib.so (Build ID: 44b7138abd5957b8d0a56ce86216d478). ``` Check whether your library (in this example somelib.so) exists in `PERFETTO_BINARY_PATH`. Then compare the Build ID to the one in your symbol file, which you can get by running `readelf -n /path/in/binary/path/somelib.so`. If it does not match, the symbolized file has a different version than the one on device, and cannot be used for symbolization. If it does, try moving somelib.so to the root of `PERFETTO_BINARY_PATH` and try again. ### Only one frame shown If you only see a single frame for functions in a specific library, make sure that the library has unwind information. We need one of * `.gnu_debugdata` * `.eh_frame` (+ preferably `.eh_frame_hdr`) * `.debug_frame`. Frame-pointer unwinding is *not supported*. To check if an ELF file has any of those, run ```console $ readelf -S file.so | grep "gnu_debugdata\|eh_frame\|debug_frame" [12] .eh_frame_hdr PROGBITS 000000000000c2b0 0000c2b0 [13] .eh_frame PROGBITS 0000000000011000 00011000 [24] .gnu_debugdata PROGBITS 0000000000000000 000f7292 ``` If this does not show one or more of the sections, change your build system to not strip them. ## (non-Android) Linux support NOTE: Do not use this for production purposes. You can use a standalone library to profile memory allocations on Linux. First [build Perfetto](/docs/contributing/build-instructions.md). You only need to do this once. ``` tools/build_all_configs.py ninja -C out/linux_clang_release ``` Then, run traced ``` out/linux_clang_release/traced ``` Start the profile (e.g. targeting trace_processor_shell) ``` tools/heap_profile -n trace_processor_shell --print-config | \ out/linux_clang_release/perfetto \ -c - --txt \ -o ~/heapprofd-trace ``` Finally, run your target (e.g. trace_processor_shell) with LD_PRELOAD ``` LD_PRELOAD=out/linux_clang_release/libheapprofd_glibc_preload.so out/linux_clang_release/trace_processor_shell ``` Then, Ctrl-C the Perfetto invocation and upload ~/heapprofd-trace to the [Perfetto UI](https://ui.perfetto.dev). NOTE: by default, heapprofd lazily initalizes to avoid blocking your program's main thread. However, if your program makes memory allocations on startup, these can be missed. To avoid this from happening, set the enironment variable `PERFETTO_HEAPPROFD_BLOCKING_INIT=1`; on the first malloc, your program will be blocked until heapprofd initializes fully but means every allocation will be correctly tracked. ## Known Issues ### {#known-issues-android11} Android 11 * 32-bit programs cannot be targeted on 64-bit devices. * Setting `sampling_interval_bytes` to 0 crashes the target process. This is an invalid config that should be rejected instead. * For startup profiles, some frame names might be missing. This will be resolved in Android 12. * `Failed to send control socket byte.` is displayed in logcat at the end of every profile. This is benign. * The object count may be incorrect in `dump_at_max` profiles. * Choosing a low shared memory buffer size and `block_client` mode might lock up the target process. ### {#known-issues-android10} Android 10 * Function names in libraries with load bias might be incorrect. Use [offline symbolization](#symbolization) to resolve this issue. * For startup profiles, some frame names might be missing. This will be resolved in Android 12. * 32-bit programs cannot be targeted on 64-bit devices. * x86 / x86_64 platforms are not supported. This includes the Android _Cuttlefish_. emulator. * On ARM32, the bottom-most frame is always `ERROR 2`. This is harmless and the callstacks are still complete. * If heapprofd is run standalone (by running `heapprofd` in a root shell, rather than through init), `/dev/socket/heapprofd` get assigned an incorrect SELinux domain. You will not be able to profile any processes unless you disable SELinux enforcement. Run `restorecon /dev/socket/heapprofd` in a root shell to resolve. * Using `vfork(2)` or `clone(2)` with `CLONE_VM` and allocating / freeing memory in the child process will prematurely end the profile. `java.lang.Runtime.exec` does this, calling it will prematurely end the profile. Note that this is in violation of the POSIX standard. * Setting `sampling_interval_bytes` to 0 crashes the target process. This is an invalid config that should be rejected instead. * `Failed to send control socket byte.` is displayed in logcat at the end of every profile. This is benign. * The object count may be incorrect in `dump_at_max` profiles. * Choosing a low shared memory buffer size and `block_client` mode might lock up the target process. ## Heapprofd vs malloc_info() vs RSS When using heapprofd and interpreting results, it is important to know the precise meaning of the different memory metrics that can be obtained from the operating system. **heapprofd** gives you the number of bytes the target program requested from the default C/C++ allocator. If you are profiling a Java app from startup, allocations that happen early in the application's initialization will not be visible to heapprofd. Native services that do not fork from the Zygote are not affected by this. **malloc\_info** is a libc function that gives you information about the allocator. This can be triggered on userdebug builds by using `am dumpheap -m /data/local/tmp/heap.txt`. This will in general be more than the memory seen by heapprofd, depending on the allocator not all memory is immediately freed. In particular, jemalloc retains some freed memory in thread caches. **Heap RSS** is the amount of memory requested from the operating system by the allocator. This is larger than the previous two numbers because memory can only be obtained in page size chunks, and fragmentation causes some of that memory to be wasted. This can be obtained by running `adb shell dumpsys meminfo ` and looking at the "Private Dirty" column. RSS can also end up being smaller than the other two if the device kernel uses memory compression (ZRAM, enabled by default on recent versions of android) and the memory of the process get swapped out onto ZRAM. | | heapprofd | malloc\_info | RSS | |---------------------|:-----------------:|:------------:|:---:| | from native startup | x | x | x | | after zygote init | x | x | x | | before zygote init | | x | x | | thread caches | | x | x | | fragmentation | | | x | If you observe high RSS or malloc\_info metrics but heapprofd does not match, you might be hitting some pathological fragmentation problem in the allocator. ## Convert to pprof You can use [traceconv](/docs/quickstart/traceconv.md) to convert the heap dumps in a trace into the [pprof](https://github.com/google/pprof) format. These can then be viewed using the pprof CLI or a UI (e.g. Speedscope, or Google-internal pprof/). ```bash tools/traceconv profile /tmp/profile ``` This will create a directory in `/tmp/` containing the heap dumps. Run: ```bash gzip /tmp/heap_profile-XXXXXX/*.pb ``` to get gzipped protos, which tools handling pprof profile protos expect. ## {#heapprofd-example-queries} Example SQL Queries We can get the callstacks that allocated using an SQL Query in the Trace Processor. For each frame, we get one row for the number of allocated bytes, where `count` and `size` is positive, and, if any of them were already freed, another line with negative `count` and `size`. The sum of those gets us the `space` view. ```sql select a.callsite_id, a.ts, a.upid, f.name, f.rel_pc, m.build_id, m.name as mapping_name, sum(a.size) as space_size, sum(a.count) as space_count from heap_profile_allocation a join stack_profile_callsite c ON (a.callsite_id = c.id) join stack_profile_frame f ON (c.frame_id = f.id) join stack_profile_mapping m ON (f.mapping = m.id) group by 1, 2, 3, 4, 5, 6, 7 order by space_size desc; ``` | callsite_id | ts | upid | name | rel_pc | build_id | mapping_name | space_size | space_count | |-------------|----|------|-------|-----------|------|--------|----------|------| |6660|5|1| malloc |244716| 8126fd.. | /apex/com.android.runtime/lib64/bionic/libc.so |106496|4| |192 |5|1| malloc |244716| 8126fd.. | /apex/com.android.runtime/lib64/bionic/libc.so |26624 |1| |1421|5|1| malloc |244716| 8126fd.. | /apex/com.android.runtime/lib64/bionic/libc.so |26624 |1| |1537|5|1| malloc |244716| 8126fd.. | /apex/com.android.runtime/lib64/bionic/libc.so |26624 |1| |8843|5|1| malloc |244716| 8126fd.. | /apex/com.android.runtime/lib64/bionic/libc.so |26424 |1| |8618|5|1| malloc |244716| 8126fd.. | /apex/com.android.runtime/lib64/bionic/libc.so |24576 |4| |3750|5|1| malloc |244716| 8126fd.. | /apex/com.android.runtime/lib64/bionic/libc.so |12288 |1| |2820|5|1| malloc |244716| 8126fd.. | /apex/com.android.runtime/lib64/bionic/libc.so |8192 |2| |3788|5|1| malloc |244716| 8126fd.. | /apex/com.android.runtime/lib64/bionic/libc.so |8192 |2| We can see all the functions are "malloc" and "realloc", which is not terribly informative. Usually we are interested in the _cumulative_ bytes allocated in a function (otherwise, we will always only see malloc / realloc). Chasing the parent_id of a callsite (not shown in this table) recursively is very hard in SQL. There is an **experimental** table that surfaces this information. The **API is subject to change**. ```sql select name, map_name, cumulative_size from experimental_flamegraph where ts = 8300973884377 and upid = 1 and profile_type = 'native' order by abs(cumulative_size) desc; ``` | name | map_name | cumulative_size | |------|----------|----------------| |__start_thread|/apex/com.android.runtime/lib64/bionic/libc.so|392608| |_ZL15__pthread_startPv|/apex/com.android.runtime/lib64/bionic/libc.so|392608| |_ZN13thread_data_t10trampolineEPKS|/system/lib64/libutils.so|199496| |_ZN7android14AndroidRuntime15javaThreadShellEPv|/system/lib64/libandroid_runtime.so|199496| |_ZN7android6Thread11_threadLoopEPv|/system/lib64/libutils.so|199496| |_ZN3art6Thread14CreateCallbackEPv|/apex/com.android.art/lib64/libart.so|193112| |_ZN3art35InvokeVirtualOrInterface...|/apex/com.android.art/lib64/libart.so|193112| |_ZN3art9ArtMethod6InvokeEPNS_6ThreadEPjjPNS_6JValueEPKc|/apex/com.android.art/lib64/libart.so|193112| |art_quick_invoke_stub|/apex/com.android.art/lib64/libart.so|193112|