modules: add simple sysinfo utility

This adds simple tiny sysinfo utility which once added
to an image will periodically report system memory utilization
every 1 second by default which can be changed by parameter.

Eventually sysinfo can be enhanced to report CPU utilization as
well.

Signed-off-by: Waldemar Kozaczuk <jwkozaczuk@gmail.com>

Author: wkozaczuk

modules/sysinfo/.gitignore

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+sysinfo*.so

modules/sysinfo/Makefile

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+INCLUDES = -I../../include
+COMMON_FLAGS = -g -Wall -fPIC $(INCLUDES) -O2
+CXXFLAGS = -std=c++11 $(COMMON_FLAGS)
+
+.PHONY: module
+module: sysinfo.so
+
+quiet = $(if $V, $1, @echo " $2"; $1)
+
+sysinfo.so: sysinfo.cc
+	$(call quiet, $(CXX) $(CXXFLAGS) -shared -o $@ sysinfo.cc, LINK $@)
+
+clean:
+	rm -f sysinfo.so sysinfo.d

modules/sysinfo/module.py

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+from osv.modules import api
+
+daemon = api.run_on_init('/sysinfo.so --interval 1000000 &!')
+default = daemon

modules/sysinfo/sysinfo.cc

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+#include <iostream>
+#include <sys/sysinfo.h>
+#include <unistd.h>
+#include <functional>
+#include <osv/options.hh>
+
+static void usage()
+{
+    std::cout << "Allowed options:\n";
+    std::cout << "  --interval arg (=1000000)   repeat every N microseconds\n";
+}
+
+static void handle_parse_error(const std::string &message)
+{
+    std::cout << message << std::endl;
+    usage();
+    exit(1);
+}
+
+int main(int ac, char** av)
+{
+    int interval_in_usecs = 1000000;
+
+    auto options_values = options::parse_options_values(ac - 1, av + 1, handle_parse_error);
+    if (options::option_value_exists(options_values, "interval")) {
+        interval_in_usecs = options::extract_option_int_value(options_values, "interval", handle_parse_error);
+    }
+
+    while (1) {
+        struct sysinfo info;
+        sysinfo(&info);
+	std::cout << "--> memory, total: " << info.totalram / 0x100000 << " MiB, used: " << 
+             (info.totalram - info.freeram) / 0x100000 << " MiB" << std::endl;
+        usleep(interval_in_usecs);
+    }
+}

modules/sysinfo/usr.manifest

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+/sysinfo.so: ${MODULE_DIR}/sysinfo.so