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Commit 550b18ca authored by Hector Dearman's avatar Hector Dearman
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Atrace: Add commandline flags to enable/disable userland tracing 

Adds a commandline flag to Atrace for Perfetto: --only_userspace.

When --only_userspace is passed atrace does everything atrace
would normally do to set up/tear down tracing (set various system
properties, poke services etc) but doesn't modify any ftrace
settings, doesn't clear read or otherwise touch the ftrace buffer,
and doesn't start or stop tracing.

Perfetto allows recording and collection of ftrace kernel events
(as systrace/atrace does for local devices). We currently integrate
with atrace to collect non-kernel events using the async_start and
async_stop command line arguments. These cause atrace to poke
binder/hal services and apps then Perfetto scrapes the print ftrace
events from the kernel ring buffer.

There are two downsides:
1. Atrace attempts drain the ftrace buffer after Perfetto has already
   done so.
2. Any time Atrace starts/stops it modifies the global ftrace settings and
   clears the ring buffer.

The second is especially unfortunate as otherwise Perfetto supports
multiplexing multiple simultaneous traces.

This flag would make it much easier to integrate atrace and Perfetto.

To test:

atest cts/hostsidetests/atrace

external/chromium-trace/systrace.py input sched

First enable ftrace:
$ adb shell 'echo 2048 > /d/tracing/buffer_size_kb'
$ adb shell 'echo > /d/tracing/trace'
$ adb shell 'echo 1 > /d/tracing/tracing_on'

Next turn on the input category.
$ adb shell atrace --async_start --only_userspace input
Touch the screen a bunch.
$ adb shell cat /d/tracing/trace
Now you should see many events.

Next turn off the input category.
$ adb shell atrace --async_stop --only_userspace
Clear tracing.
$ adb shell 'echo > /d/tracing/trace'
Touch the screen a bunch.
$ adb shell cat /d/tracing/trace
You should see no events.

Ftrace settings should not have been touched:
$ adb shell cat /d/tracing/tracing_on
Should be 1 still.
$ adb shell cat /d/tracing/buffer_size_kb
Should be 2048 still.

Bug: 73625407
Test: see above.
Change-Id: Ia43ab689c4f93280315eb984581187c1582c2b07
Merged-In: Ia43ab689c4f93280315eb984581187c1582c2b07
parent 9cab7ee1

cmds/atrace/atrace.cpp

+71 −38
Original line number Diff line number Diff line
@@ -774,22 +774,10 @@ static bool setCategoriesEnableFromFile(const char* categories_file) 
    return ok;

}



// Set all the kernel tracing settings to the desired state for this trace

// capture.

static bool setUpTrace()

static bool setUpUserspaceTracing()

{

    bool ok = true;



    // Set up the tracing options.

    ok &= setCategoriesEnableFromFile(g_categoriesFile);

    ok &= setTraceOverwriteEnable(g_traceOverwrite);

    ok &= setTraceBufferSizeKB(g_traceBufferSizeKB);

    // TODO: Re-enable after stabilization

    //ok &= setCmdlineSize();

    ok &= setClock();

    ok &= setPrintTgidEnableIfPresent(true);

    ok &= setKernelTraceFuncs(g_kernelTraceFuncs);



    // Set up the tags property.

    uint64_t tags = 0;

    for (size_t i = 0; i < arraysize(k_categories); i++) {
@@ -827,6 +815,37 @@ static bool setUpTrace() 
        ok &= ServiceUtility::PokeServices();

    }



    return ok;

}



static void cleanUpUserspaceTracing()

{

    setTagsProperty(0);

    clearAppProperties();

    pokeBinderServices();



    if (g_tracePdx) {

        ServiceUtility::PokeServices();

    }

}





// Set all the kernel tracing settings to the desired state for this trace

// capture.

static bool setUpKernelTracing()

{

    bool ok = true;



    // Set up the tracing options.

    ok &= setCategoriesEnableFromFile(g_categoriesFile);

    ok &= setTraceOverwriteEnable(g_traceOverwrite);

    ok &= setTraceBufferSizeKB(g_traceBufferSizeKB);

    // TODO: Re-enable after stabilization

    //ok &= setCmdlineSize();

    ok &= setClock();

    ok &= setPrintTgidEnableIfPresent(true);

    ok &= setKernelTraceFuncs(g_kernelTraceFuncs);



    // Disable all the sysfs enables.  This is done as a separate loop from

    // the enables to allow the same enable to exist in multiple categories.

    ok &= disableKernelTraceEvents();
@@ -854,20 +873,11 @@ static bool setUpTrace() 
}



// Reset all the kernel tracing settings to their default state.

static void cleanUpTrace()

static void cleanUpKernelTracing()

{

    // Disable all tracing that we're able to.

    disableKernelTraceEvents();



    // Reset the system properties.

    setTagsProperty(0);

    clearAppProperties();

    pokeBinderServices();



    if (g_tracePdx) {

        ServiceUtility::PokeServices();

    }



    // Set the options back to their defaults.

    setTraceOverwriteEnable(true);

    setTraceBufferSizeKB(1);
@@ -875,7 +885,6 @@ static void cleanUpTrace() 
    setKernelTraceFuncs(NULL);

}





// Enable tracing in the kernel.

static bool startTrace()

{
@@ -1107,6 +1116,7 @@ int main(int argc, char **argv) 
    bool traceStop = true;

    bool traceDump = true;

    bool traceStream = false;

    bool onlyUserspace = false;



    if (argc == 2 && 0 == strcmp(argv[1], "--help")) {

        showHelp(argv[0]);
@@ -1125,6 +1135,7 @@ int main(int argc, char **argv) 
            {"async_start",       no_argument, 0,  0 },

            {"async_stop",        no_argument, 0,  0 },

            {"async_dump",        no_argument, 0,  0 },

            {"only_userspace",    no_argument, 0,  0 },

            {"list_categories",   no_argument, 0,  0 },

            {"stream",            no_argument, 0,  0 },

            {           0,                  0, 0,  0 }
@@ -1197,6 +1208,8 @@ int main(int argc, char **argv) 
                    async = true;

                    traceStart = false;

                    traceStop = false;

                } else if (!strcmp(long_options[option_index].name, "only_userspace")) {

                    onlyUserspace = true;

                } else if (!strcmp(long_options[option_index].name, "stream")) {

                    traceStream = true;

                    traceDump = false;
@@ -1214,6 +1227,14 @@ int main(int argc, char **argv) 
        }

    }



    if (onlyUserspace) {

        if (!async || !(traceStart || traceStop)) {

            fprintf(stderr, "--only_userspace can only be used with "

                    "--async_start or --async_stop\n");

            exit(1);

        }

    }



    registerSigHandler();



    if (g_initialSleepSecs > 0) {
@@ -1221,13 +1242,19 @@ int main(int argc, char **argv) 
    }



    bool ok = true;



    if (traceStart) {

        ok &= setUpTrace();

        ok &= setUpUserspaceTracing();

    }



    if (ok && traceStart && !onlyUserspace) {

        ok &= setUpKernelTracing();

        ok &= startTrace();

    }



    if (ok && traceStart) {

        if (!traceStream) {



        if (!traceStream && !onlyUserspace) {

            printf("capturing trace...");

            fflush(stdout);

        }
@@ -1237,9 +1264,12 @@ int main(int argc, char **argv) 
        // contain entries from only one CPU can cause "begin" entries without a

        // matching "end" entry to show up if a task gets migrated from one CPU to

        // another.

        if (!onlyUserspace)

            ok = clearTrace();



        if (!onlyUserspace)

            writeClockSyncMarker();



        if (ok && !async && !traceStream) {

            // Sleep to allow the trace to be captured.

            struct timespec timeLeft;
@@ -1258,10 +1288,10 @@ int main(int argc, char **argv) 
    }



    // Stop the trace and restore the default settings.

    if (traceStop)

    if (traceStop && !onlyUserspace)

        stopTrace();



    if (ok && traceDump) {

    if (ok && traceDump && !onlyUserspace) {

        if (!g_traceAborted) {

            printf(" done\n");

            fflush(stdout);
@@ -1288,8 +1318,11 @@ int main(int argc, char **argv) 
    }



    // Reset the trace buffer size to 1.

    if (traceStop)

        cleanUpTrace();

    if (traceStop) {

        cleanUpUserspaceTracing();

        if (!onlyUserspace)

            cleanUpKernelTracing();

    }



    return g_traceAborted ? 1 : 0;

}