--- /dev/null
+.TH CHOOM 1 "April 2018" "util-linux" "User Commands"
+.SH NAME
+choom \- display and adjust OOM-killer score.
+.SH SYNOPSIS
+.B choom
+.RB \-p
+.IR pid
+.sp
+.B choom
+.RB \-p
+.IR pid
+.RB \-n
+.IR number
+.sp
+.B choom
+.RB \-n
+.IR number
+.IR command\ [ argument ...]
+
+.SH DESCRIPTION
+The \fBchoom\fP command displays and adjusts Out-Of-Memory killer score setting.
+
+.SH OPTIONS
+.TP
+.BR \-p ", " \-\-pid " \fIpid\fP
+Specifies process ID.
+.TP
+.BR \-n , " \-\-adjust " \fIvalue\fP
+Specify the adjust score value.
+.TP
+.BR \-h ", " \-\-help
+Display help text and exit.
+.TP
+.BR \-V ", " \-\-version
+Display version information and exit.
+.SH NOTES
+Linux kernel uses the badness heuristic to select which process gets killed in
+out of memory conditions.
+
+The badness heuristic assigns a value to each candidate task ranging from 0
+(never kill) to 1000 (always kill) to determine which process is targeted. The
+units are roughly a proportion along that range of allowed memory the process
+may allocate from based on an estimation of its current memory and swap use.
+For example, if a task is using all allowed memory, its badness score will be
+1000. If it is using half of its allowed memory, its score will be 500.
+
+There is an additional factor included in the badness score: the current memory
+and swap usage is discounted by 3% for root processes.
+
+The amount of "allowed" memory depends on the context in which the oom killer
+was called. If it is due to the memory assigned to the allocating task's cpuset
+being exhausted, the allowed memory represents the set of mems assigned to that
+cpuset. If it is due to a mempolicy's node(s) being exhausted, the allowed
+memory represents the set of mempolicy nodes. If it is due to a memory
+limit (or swap limit) being reached, the allowed memory is that configured
+limit. Finally, if it is due to the entire system being out of memory, the
+allowed memory represents all allocatable resources.
+
+The adjust score value is added to the badness score before it is used to
+determine which task to kill. Acceptable values range from -1000 to +1000.
+This allows userspace to polarize the preference for oom killing either by
+always preferring a certain task or completely disabling it. The lowest
+possible value, -1000, is equivalent to disabling oom killing entirely for that
+task since it will always report a badness score of 0.
+
+Setting a adjust score value of +500, for example, is roughly equivalent to
+allowing the remainder of tasks sharing the same system, cpuset, mempolicy, or
+memory controller resources to use at least 50% more memory. A value of -500,
+on the other hand, would be roughly equivalent to discounting 50% of the task's
+allowed memory from being considered as scoring against the task.
+
+.SH AUTHORS
+.nf
+Karel Zak <kzak@redhat.com>
+.fi
+.SH SEE ALSO
+.BR proc (5)
+.SH AVAILABILITY
+The \fBchoom\fP command is part of the util-linux package and is available from
+.UR https://\:www.kernel.org\:/pub\:/linux\:/utils\:/util-linux/
+Linux Kernel Archive
+.UE .
--- /dev/null
+/*
+ * 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;
+}
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