Update ReadMe.md with Example about "How to use this profile on remote JVM" about async-profiler

[apangin]

@egor-ryashin Could you please open a separate issue?

[apangin]

You can dynamically inject agent library into the running JVM using HotSpot Attach API.
For instance, you can do this with my jattach utility:

jattach PID load /path/to/libasyncProfiler.so true start
jattach PID load /path/to/libasyncProfiler.so true stop

[leventov]

@apangin I've followed this and it just prints

Connected to remote JVM
Response Code = -1

[apangin]

This means the command was recognized, but the library could not be loaded.
Make sure you specify the absolute path to the library, and the file has proper permissions.

[tartemov]

I'm trying to attach and dump summary info:
$ ./jattach $PID load /tmp/libasyncProfiler.so true start 1 10 Connected to remote JVM Response code = 0 0 $ ./jattach $PID load /tmp/libasyncProfiler.so true dumpRawTraces Connected to remote JVM Response code = 0 0 $ ./jattach $PID load /tmp/libasyncProfiler.so true stop Connected to remote JVM Response code = 0 0 $ ./jattach $PID load /tmp/libasyncProfiler.so true dumpRawTraces Connected to remote JVM Response code = 0 0
but I can't get any methods info. What am I doing wrong?

[apangin]

Note that profiling stats are printed on stdout of Java process (not on the console of jattach).

[apangin]

Alternatively you may dump raw traces to the specified file:

./jattach $PID load /tmp/libasyncProfiler.so true dumpRawTraces:/path/to/profile.txt

[tartemov]

Thanks. With dumpRawTraces method it's working fine. But with other methods - summary, dumpMethods and others it doesn't work - no file created.

[tartemov]

Hi again! Could you please get any advice how to get summary/dumpMethods info in file?

[apangin]

This is not supported right now, but will get fixed soon.

[balmaster]

@tartemov you can use Brendan Gregg scripts to fold stacks and make svg

1. clone https://github.com/brendangregg/FlameGraph

2. FlameGraph/stackcollapse-ljp.awk mytrace.txt > mytrace.folded

3. FlameGraph/flamegraph.pl mytrace.folded > mytrace.svg

[apangin]

Resolved by #13

[egor-ryashin]

I cannot attach to some JVM processes.
I made profiler.sh output more info:

    collect)
        $JATTACH $PID load $PROFILER true start,file=$FILE$INTERVAL$FRAMEBUF #> /dev/null
        if [ $? -ne 0 ]; then
            exit 1
        fi

Got this:

~/async-profiler $ sudo -u xncore ./profiler.sh -d 10 3515
Connected to remote JVM
Response code = -1

Is there a way to debug it further?