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Commit 56a2ba0b authored by Carmen Jackson's avatar Carmen Jackson
Browse files

Set the atrace clock to boot when possible and mono otherwise. 

Bug: 32379831
Test: Inspected the trace_clock while running atrace, without including the .rc file change:
$ adb shell
marlin:/ # cat /d/tracing/trace_clock
[local] global counter uptime perf mono boot
marlin:/ # atrace --async_start freq
capturing trace...
marlin:/ # cat /d/tracing/trace_clock
local global counter uptime perf mono [boot]
marlin:/ # atrace --async_stop > /dev/null
marlin:/ # cat /d/tracing/trace_clock
local global counter uptime perf mono [boot]
marlin:/ # exit

Test: Inspected the trace_clock while running atrace, after the .rc file change:
$ adb shell
marlin:/ # cat /d/tracing/trace_clock
local global counter uptime perf mono [boot]
marlin:/ # atrace --async_start freq
capturing trace...
marlin:/ # cat /d/tracing/trace_clock
local global counter uptime perf mono [boot]

Change-Id: I9ec88df109b311b90c9d88fe3a70f9ce090b4d15
parent 03d95980

cmds/atrace/atrace.cpp

+33 −9
Original line number Diff line number Diff line
@@ -450,8 +450,8 @@ static bool isTraceClock(const char *mode) 
        return false;

    }



    char buf[4097];

    ssize_t n = read(fd, buf, 4096);

    char buf[100];

    ssize_t n = read(fd, buf, 99);

    close(fd);

    if (n == -1) {

        fprintf(stderr, "error reading %s: %s (%d)\n", k_traceClockPath,
@@ -475,13 +475,38 @@ static bool isTraceClock(const char *mode) 
    return strcmp(mode, start) == 0;

}



// Enable or disable the kernel's use of the global clock.  Disabling the global

// clock will result in the kernel using a per-CPU local clock.

// Read the trace_clock sysfs file and return true if it contains the requested

// value.  The trace_clock file format is:

// local [global] counter uptime perf

static bool traceClockContains(const char *mode)

{

    int fd = open((g_traceFolder + k_traceClockPath).c_str(), O_RDONLY);

    if (fd == -1) {

        fprintf(stderr, "error opening %s: %s (%d)\n", k_traceClockPath,

            strerror(errno), errno);

        return false;

    }



    char buf[100];

    ssize_t n = read(fd, buf, 99);

    close(fd);

    if (n == -1) {

        fprintf(stderr, "error reading %s: %s (%d)\n", k_traceClockPath,

            strerror(errno), errno);

        return false;

    }

    buf[n] = '\0';



    return strstr(buf, mode) != NULL;

}



// Set the clock to the best available option while tracing. Use 'boot' if it's

// available; otherwise, use 'mono'.

// Any write to the trace_clock sysfs file will reset the buffer, so only

// update it if the requested value is not the current value.

static bool setGlobalClockEnable(bool enable)

static bool setClock()

{

    const char *clock = enable ? "global" : "local";

    const char* clock = traceClockContains("boot") ? "boot" : "mono";



    if (isTraceClock(clock)) {

        return true;
@@ -783,7 +808,7 @@ static bool setUpTrace() 
    ok &= setCategoriesEnableFromFile(g_categoriesFile);

    ok &= setTraceOverwriteEnable(g_traceOverwrite);

    ok &= setTraceBufferSizeKB(g_traceBufferSizeKB);

    ok &= setGlobalClockEnable(true);

    ok &= setClock();

    ok &= setPrintTgidEnableIfPresent(true);

    ok &= setKernelTraceFuncs(g_kernelTraceFuncs);
@@ -859,7 +884,6 @@ static void cleanUpTrace() 
    // Set the options back to their defaults.

    setTraceOverwriteEnable(true);

    setTraceBufferSizeKB(1);

    setGlobalClockEnable(false);

    setPrintTgidEnableIfPresent(false);

    setKernelTraceFuncs(NULL);

}
@@ -1210,7 +1234,7 @@ int main(int argc, char **argv) 


    if (ok && traceStart) {

        if (!traceStream) {

            printf("capturing trace...");

            printf("capturing trace...\n");

            fflush(stdout);

        }

cmds/atrace/atrace.rc

+4 −0
Original line number Diff line number Diff line
@@ -124,6 +124,10 @@ on post-fs 
    write /sys/kernel/debug/tracing/tracing_on 0

    write /sys/kernel/tracing/tracing_on 0



    # Set the trace clock to boot if it exists, falling back to mono if not.

    write /d/tracing/trace_clock mono

    write /d/tracing/trace_clock boot



# Allow only the shell group to read and truncate the kernel trace.

    chown root shell /sys/kernel/debug/tracing/trace

    chown root shell /sys/kernel/tracing/trace