diff options
Diffstat (limited to 'simpleperf/doc/README.md')
| -rw-r--r-- | simpleperf/doc/README.md | 19 |
1 files changed, 16 insertions, 3 deletions
diff --git a/simpleperf/doc/README.md b/simpleperf/doc/README.md index f0cddd2a..2f3b0854 100644 --- a/simpleperf/doc/README.md +++ b/simpleperf/doc/README.md @@ -20,8 +20,9 @@ The latest document is [here](https://android.googlesource.com/platform/system/e - [Executable commands reference](#executable-commands-reference) - [Scripts reference](#scripts-reference) - [Answers to common issues](#answers-to-common-issues) - - [Why we suggest profiling on Android >= N devices?](#why-we-suggest-profiling-on-android-gt-n-devices) + - [Why we suggest profiling on Android >= N devices?](#why-we-suggest-profiling-on-android--n-devices) - [Suggestions about recording call graphs](#suggestions-about-recording-call-graphs) + - [Why we can't always get complete DWARF-based call graphs](#why-we-cant-always-get-complete-dwarf-based-call-graphs) - [How to solve missing symbols in report?](#how-to-solve-missing-symbols-in-report) - [Fix broken callchain stopped at C functions](#fix-broken-callchain-stopped-at-c-functions) - [Show annotated source code and disassembly](#show-annotated-source-code-and-disassembly) @@ -88,7 +89,7 @@ bin/${host}/${arch}/simpleperf: simpleperf executables used on the host, only su bin/${host}/${arch}/libsimpleperf_report.${so/dylib/dll}: report shared libraries used on the host. -*.py, inferno: Python scripts used for recording and reporting. +*.py, inferno, purgatorio: Python scripts used for recording and reporting. Details are in [scripts_reference.md](scripts_reference.md). ## Android application profiling @@ -159,6 +160,18 @@ graphs. It can be supported in two ways: 1. Use unstripped native binaries when building the apk, as [here](https://android.googlesource.com/platform/system/extras/+/master/simpleperf/demo/SimpleperfExampleWithNative/app/profiling.gradle). 2. Download unstripped native libraries on device, as [here](#fix-broken-callchain-stopped-at-c-functions). +### Why we can't always get complete DWARF-based call graphs? + +DWARF-based call graphs are generated by unwinding thread stacks. When a sample is generated, up to +64KB stack data is dumped by the kernel. By unwinding the stack based on dwarf information, we get +a callchain. But the thread stack can be much longer than 64KB. In that case, we can't unwind to +the thread start point. + +To alleviate the problem, simpleperf joins callchains after recording them. If two callchains of +a thread have an entry containing the same ip and sp address, then simpleperf tries to join them to +make the callchains longer. In that case, the longer we run, the more samples we get. This makes it +more likely to get complete callchains, but it's still not guaranteed to get complete call graphs. + ### How to solve missing symbols in report? The simpleperf record command collects symbols on device in perf.data. But if the native libraries @@ -233,7 +246,7 @@ Patches can be uploaded to android-review.googlesource.com as [here](https://sou or sent to email addresses listed [here](https://android.googlesource.com/platform/system/extras/+/master/simpleperf/OWNERS). If you want to compile simpleperf C++ source code, follow below steps: -1. Download AOSP master branch as [here](https://source.android.com/setup/build/requirements). +1. Download AOSP main branch as [here](https://source.android.com/setup/build/requirements). 2. Build simpleperf. ```sh $ . build/envsetup.sh |