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https://github.com/async-profiler/async-profiler.git
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96 lines
3.1 KiB
Markdown
96 lines
3.1 KiB
Markdown
# Profiling Non-Java applications
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The scope of profiling non-Java applications is limited to the case when profiler is controlled
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programmatically from the process being profiled or with `LD_PRELOAD`. It is worth noting that
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[dynamic attach](IntegratingAsyncProfiler.md#launching-as-an-agent)
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which is available for Java is not supported for non-Java profiling.
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## LD_PRELOAD
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async-profiler can be injected into a native application through the `LD_PRELOAD` mechanism:
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```
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LD_PRELOAD=/path/to/libasyncProfiler.so ASPROF_COMMAND=start,event=cpu,file=profile.jfr NativeApp [args]
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```
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All basic functionality remains the same. Profiler can run in `cpu`, `wall`, `nativemem` and other perf_events
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modes. Flame Graph and JFR output formats are supported, although JFR files will obviously lack
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Java-specific events.
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See [Profiling Modes](ProfilingModes.md) for more examples.
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## Controlling async-profiler via the C API
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Similar to the
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[Java API](IntegratingAsyncProfiler.md#using-java-api),
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there is a C API for using profiler inside a native application.
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Header file for the API is bundled in the async-profiler release package under [`include/asprof.h`](../src/asprof.h).
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To use it in a C/C++ application, include the mentioned `asprof.h`. Below is an example showing how to invoke async-profiler with the API:
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```
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#include "asprof.h"
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#include <dlfcn.h>
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#include <stdio.h>
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#include <stdlib.h>
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void test_output_callback(const char* buffer, size_t size) {
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fwrite(buffer, sizeof(char), size, stderr);
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}
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int main() {
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void* lib = dlopen("/path/to/libasyncProfiler.so", RTLD_NOW);
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if (lib == NULL) {
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printf("%s\n", dlerror());
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exit(1);
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}
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asprof_init_t asprof_init = (asprof_init_t)dlsym(lib, "asprof_init");
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asprof_execute_t asprof_execute = (asprof_execute_t)dlsym(lib, "asprof_execute");
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asprof_error_str_t asprof_error_str = (asprof_error_str_t)dlsym(lib, "asprof_error_str");
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if (asprof_init == NULL || asprof_execute == NULL || asprof_error_str == NULL) {
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printf("%s\n", dlerror());
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dlclose(lib);
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exit(1);
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}
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asprof_init();
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printf("Starting profiler\n");
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char cmd[] = "start,event=cpu,loglevel=debug,file=profile.jfr";
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asprof_error_t err = asprof_execute(cmd, test_output_callback);
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if (err != NULL) {
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fprintf(stderr, "%s\n", asprof_error_str(err));
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exit(1);
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}
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// ... some meaningful work ...
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printf("Stopping profiler\n");
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err = asprof_execute("stop", test_output_callback);
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if (err != NULL) {
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fprintf(stderr, "%s\n", asprof_error_str(err));
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exit(1);
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}
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return 0;
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}
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```
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## Unstable APIs
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These APIs are unstable and might change or be removed in the next version of async-profiler.
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### Advanced Sampling
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The `asprof_get_thread_local_data` function returns a pointer to async-profiler's
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thread-local data structure. The structure is guaranteed to live as long as the thread.
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The returned structure contains a pointer that increments every time there is a sample. This gives
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native code an easy way to detect when a sample event had occurred, and to log metadata about what the
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program was doing when the event happened.
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