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OSv

Building

First, install prerequisite packages:

Fedora

yum install ant autoconf automake boost-static gcc-c++ genromfs libvirt libtool flex bison

Debian

apt-get install build-essential libboost-all-dev genromfs autoconf libtool openjdk-7-jdk ant

Ubuntu users: you may use Oracle JDK if you don't want to pull too many dependencies for openjdk-7-jdk

To ensure functional C++11 support, Gcc 4.7 or above is required. Gcc 4.8 or above is recommended, as this was the first version to fully comply with the C++11 standard.

Make sure all git submodules are up-to-date:

git submodule update --init

Finally, build everything at once:

make external all

By default make creates image in qcow2 format. To change this pass format value via img_format variable, i.e.

make img_format=raw external all

Running OSv

./scripts/run.py

By default, this runs OSv under KVM, with 4 VCPUs and 1GB of memory, and runs the default management application (containing a shell, Web server, and SSH server).

If running under KVM you can terminate by hitting Ctrl+A X.

External Networking

To start osv with external networking:

sudo ./scripts/run.py -n -v

The -v is for kvm's vhost that provides better performance and it's setup requires a tap and thus we use sudo.

By default OSv spawns a dhcpd that auto config the virtual nics. Static config can be done within OSv, configure networking like so:

ifconfig virtio-net0 192.168.122.100 netmask 255.255.255.0 up
route add default gw 192.168.122.1

Test networking:

test TCPExternalCommunication

Running Java or C applications that already reside within the image:

# The default Java-based shell and web server
sudo scripts/run.py -nv -m4G -e "java.so -jar /usr/mgmt/web-1.0.0.jar app prod"

# One of the unit tests (compiled C++ code)
$ sudo scripts/run.py -nv -m4G -e "/tests/tst-pipe.so"

Debugging

To build with debugging symbols, and preemption off (to not confuse gdb),

make mode=debug conf-preempt=0

To clean debugging build's results, use

make clean mode=debug

To run the debugging build:

./scripts/run.py -d

To connect a debugger to this run:

$ gdb build/debug/loader.elf
(gdb) connect
(gdb) osv syms
(gdb) bt

To put a breakpoint early in the osv run, a useful trick is tell the vm to reboot after setting the breakpoint:

(gdb) hbreak function_name
(gdb) monitor system_reset
(gdb) c

Tracing

To add a static tracepoint, use the following code:

tracepoint<u64, int> trace_foo("foo", "x=%x y=%d");

void foo(u64 x, int y)
{
    trace_foo(x, y);

    // ...
}

where:

trace_foo: an internal identifier
"foo": a name for the tracepoint as will be visible in the log
<u64, int>: parameters for the tracepoint
"x=%x y=%d": format string for the tracepoint; size modifiers unneeded

To enable tracepoints at runtime, use the --trace= switch:

scripts/imgedit.py setargs  build/release/loader.img --trace=sched\* testrunner.so

you can use multiple --trace= switches, or a single one with commas. Shell-style wildcards allow enabling multiple tracepoints (as in the example).

If you add the --trace-backtrace switch, every tracepoint hit will also record a stack backtrace.

To trace all function entries/returns in the program, build with conf-tracing=1 (clean build needed), and enable "function*" tracepoints, with --trace=.

To view a trace, connect with gdb, and:

(gdb) osv syms
(gdb) set pagination off
(gdb) set logging on
(gdb) osv trace

gdb.txt will contain the the trace.

Leak Detection

Memory allocation tracking can be enabled/disabled with the gdb commands "osv leak on", "osv leak off", but even easier is to add the "--leak" parameter to the loader, to have it start leak detection when entering the payload (not during OSv boot). For example:

scripts/run.py -e "--leak java.so -jar cli.jar"

scripts/run.py -e "--leak tests/tst-leak.so"

Leak detection can be used in either the debug or release build, though note that the release builds' optimizations may somewhat modify the reported call traces.

When the run ends, connect to OSV with the debugger to see the where the remaining allocation come from:

$ gdb build/release/loader.elf       # or build/debug/loader.elf
(gdb) connect
(gdb) osv syms
(gdb) set logging on	# optional, if you want to save the output to a file
(gdb) set height 0	# optional, useful if using "set logging on"
(gdb) osv leak show

Please note that "osv leak show" can take a L-O-N-G time - even a few minutes, especially when running Java, as it allocates myriads of objects that GDB will now have to inspect.

Use-after-free and overrun detection

Set conf-debug_memory=1 in base.mak, and perform a clean build. A use-after-free will result in an immediate segmentation fault.

Note that the detector requires a lot of memory, so you may need to start a larger guest.

Running Java benchmarks

After running "make", do

./scripts/run.py -e "java.so -jar /tests/bench/bench.jar"

Profiling

You can use perf kvm for profiling:

perf kvm --guestvmlinux=build/release/loader.elf top