choom: new command to adjust OOM-killer score value

Let's provide command line tool, man page with OOM description and
bash-completion. It seems better than force end-users to use "echo"
to /proc.

Addresses: https://github.com/karelzak/util-linux/issues/609
Signed-off-by: Karel Zak <kzak@redhat.com>

1 files changed, 150 insertions, 0 deletions

diff --git a/sys-utils/choom.c b/sys-utils/choom.c
new file mode 100644
index 000000000..080267f91
--- /dev/null
+++ b/sys-utils/choom.c
@@ -0,0 +1,150 @@
+/*
+ * choom - Change OOM score setting
+ *
+ * Copyright (C) 2018 Karel Zak <kzak@redhat.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it would be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <getopt.h>
+#include <errno.h>
+
+#include <linux/oom.h>
+
+#include "nls.h"
+#include "c.h"
+#include "path.h"
+#include "strutils.h"
+#include "closestream.h"
+
+static void __attribute__((__noreturn__)) usage(void)
+{
+	FILE *out = stdout;
+	fputs(USAGE_HEADER, out);
+	fprintf(out,
+	      _(" %1$s [options] -p pid\n"
+		" %1$s [options] -n number -p pid\n"
+		" %1$s [options] -n number command [args...]]\n"),
+		program_invocation_short_name);
+
+	fputs(USAGE_SEPARATOR, out);
+	fputs(_("Display and adjust OOM-killer score.\n"), out);
+
+	fputs(USAGE_OPTIONS, out);
+	fputs(_(" -n, --adjust <num>     specify the adjust score value\n"), out);
+	fputs(_(" -p, --pid <num>        process ID\n"), out);
+	fputs(USAGE_SEPARATOR, out);
+	printf(USAGE_HELP_OPTIONS(24));
+	printf(USAGE_MAN_TAIL("choom(1)"));
+	exit(EXIT_SUCCESS);
+}
+
+static int get_score(const pid_t pid)
+{
+	return path_read_s32("/proc/%d/oom_score", (int) pid);
+}
+
+static int get_score_adj(const pid_t pid)
+{
+	return path_read_s32("/proc/%d/oom_score_adj", (int) pid);
+}
+
+static int set_score_adj(const pid_t pid, int adj)
+{
+	char buf[sizeof(stringify_value(OOM_SCORE_ADJ_MIN))];
+
+	snprintf(buf, sizeof(buf), "%d", adj);
+
+	if (path_write_str(buf, "/proc/%d/oom_score_adj", (int) pid) < 0)
+		return -1;
+	return 0;
+}
+
+int main(int argc, char **argv)
+{
+	pid_t pid = 0;
+	int c, adj = 0, has_adj = 0;
+
+	static const struct option longopts[] = {
+		{ "adjust",  required_argument, NULL, 'n' },
+		{ "pid",     required_argument, NULL, 'p' },
+		{ "help",    no_argument,       NULL, 'h' },
+		{ "version", no_argument,       NULL, 'V' },
+		{ NULL,      0,                 NULL,  0  }
+	};
+
+	setlocale(LC_ALL, "");
+	bindtextdomain(PACKAGE, LOCALEDIR);
+	textdomain(PACKAGE);
+	atexit(close_stdout);
+
+	while ((c = getopt_long(argc, argv, "hn:p:V", longopts, NULL)) != -1) {
+		switch (c) {
+		case 'p':
+			pid = strtos32_or_err(optarg, _("invalid PID argument"));
+			break;
+		case 'n':
+			adj = strtos32_or_err(optarg, _("invalid adjust argument"));
+			has_adj = 1;
+			break;
+		case 'V':
+			printf(UTIL_LINUX_VERSION);
+			return EXIT_SUCCESS;
+		case 'h':
+			usage();
+		default:
+			errtryhelp(EXIT_FAILURE);
+		}
+	}
+
+	if (optind < argc && pid) {
+		warnx(_("invalid argument: %s"), argv[optind]);
+		errtryhelp(EXIT_FAILURE);
+	}
+	if (!pid && argc - optind < 1) {
+		warnx(_("no PID or COMMAND specified"));
+		errtryhelp(EXIT_FAILURE);
+	}
+	if (optind < argc && !has_adj) {
+		warnx(_("no OOM score adjust value specified"));
+		errtryhelp(EXIT_FAILURE);
+	}
+
+	/* Show */
+	if (!has_adj) {
+		printf(_("pid %d's current OOM score: %d\n"), pid, get_score(pid));
+		printf(_("pid %d's current OOM score adjust value: %d\n"), pid, get_score_adj(pid));
+
+	/* Change */
+	} else if (pid) {
+		int old = get_score_adj(pid);
+
+		if (set_score_adj(pid, adj))
+			err(EXIT_FAILURE, _("failed to set score adjust value"));
+
+		printf(_("pid %d's OOM score adjust value changed from %d to %d\n"), pid, old, adj);
+
+	/* Start new process */
+	} else {
+		argv += optind;
+		execvp(argv[0], argv);
+		errexec(argv[0]);
+	}
+
+	return EXIT_SUCCESS;
+}