This is nohang config file. Lines starting with #, tabs and spaces are comments. The configuration includes the following sections: 1. Memory levels to respond to as an OOM threat 2. The frequency of checking the level of available memory (and CPU usage) 3. The prevention of killing innocent victims 4. Impact on the badness of processes via matching their names with regular expressions 5. The execution of a specific command instead of sending the SIGTERM signal 6. GUI notifications: - results of preventing OOM - low memory warnings 7. Preventing the slowing down of the program 8. Output verbosity Just read the description of the parameters and edit the values. Please restart the program after editing the config. ##################################################################### 1. Thresholds below which a signal should be sent to the victim Sets the available memory levels below which SIGTERM or SIGKILL signals are sent. The signal will be sent if MemAvailable and SwapFree (in /proc/meminfo) at the same time will drop below the corresponding values. Can be specified in % (percent) and M (MiB). Valid values are floating-point numbers from the range [0; 100] %. MemAvailable levels. mem_min_sigterm = 9 % mem_min_sigkill = 6 % SwapFree levels. swap_min_sigterm = 9 % swap_min_sigkill = 6 % Specifying the total share of zram in memory, if exceeded the corresponding signals are sent. As the share of zram in memory increases, it may fall responsiveness of the system. 90 % is a usual hang level, not recommended to set very high. Can be specified in % and M. Valid values are floating-point numbers from the range [0; 100] %. zram_max_sigterm = 50 % zram_max_sigkill = 55 % ##################################################################### 2. The frequency of checking the amount of available memory (and CPU usage) Coefficients that affect the intensity of monitoring. Reducing the coefficients can reduce CPU usage and increase the periods between memory checks. Why three coefficients instead of one? Because the swap fill rate is usually lower than the RAM fill rate. It is possible to set a lower intensity of monitoring for swap without compromising to prevent OOM and thus reduce the CPU load. Default values are well for desktop. On servers without rapid fluctuations in memory levels the values can be reduced. Valid values are positive floating-point numbers. rate_mem = 6 rate_swap = 3 rate_zram = 1 ##################################################################### 3. The prevention of killing innocent victims Минимальное значение oom_score, которым должен обладать процесс для того, чтобы ему был отправлен сигнал. Позволяет предотвратить убийство невиновных если что-то пойдет не так. Valid values are integers from the range [0; 1000]. min_badness = 10 Минимальная задержка после отправки соответствующих сигналов для предотвращения риска убийства сразу множества процессов. Valid values are non-negative floating-point numbers. min_delay_after_sigterm = 0.5 min_delay_after_sigkill = 3 Процессы браузера chromium обычно имеют oom_score_adj 200 или 300. Это приводит к тому, что процессы хрома умирают первыми вместо действительно тяжелых процессов. Если параметр decrease_oom_score_adj установлен в значение True, то у процессов, имеющих oom_score_adj выше oom_score_adj_max значение oom_score_adj будет опущено до oom_score_adj_max перед поиском жертвы. Enabling the option requires root privileges. Valid values are True and False. Values are case sensitive. decrease_oom_score_adj = False Valid values are integers from the range [0; 1000]. oom_score_adj_max = 20 ##################################################################### 4. Impact on the badness of processes via matching their names with regular expressions. See https://en.wikipedia.org/wiki/Regular_expression and https://en.wikipedia.org/wiki/Perl_Compatible_Regular_Expressions Enabling this option slows down the search for the victim because the names of all processes are compared with the specified regex patterns. Valid values are True and False. regex_matching = False Badness of processes whose names correspond to prefer_regex will be calculated by the following formula: badness = (oom_score + 1) * prefer_factor prefer_regex = tail|python3 Valid values are floating-point numbers from the range [1; 1000]. prefer_factor = 3 Badness of processes whose names correspond to avoid_regex will be calculated by the following formula: badness = oom_score / avoid_factor avoid_regex = Xorg|sshd Valid values are floating-point numbers from the range [1; 1000]. avoid_factor = 3 ##################################################################### 5. The execution of a specific command instead of sending the SIGTERM signal. For processes with a specific name you can specify a command to run instead of sending the SIGTERM signal. For example, if the process is running as a daemon, you can run the restart command instead of sending SIGTERM. Valid values are True and False. execute_the_command = False The length of the process name can't exceed 15 characters. The syntax is as follows: lines starting with keyword $ETC are considered as the lines containing names of processes and corresponding commands. After a name of process the triple slash (///) follows. And then follows the command that will be executed if the specified process is selected as a victim. The ampersand (&) at the end of the command will allow nohang to continue runing without waiting for the end of the command execution. For example: $ETC mysqld /// systemctl restart mariadb.service & $ETC php-fpm7.0 /// systemctl restart php7.0-fpm.service $ETC proc_name /// some command ##################################################################### 6. GUI notifications: - results of preventing OOM - low memory warnings Включение этой опции требует наличия notify-send в системе. В Debian/Ubuntu это обеспечивается установкой пакета libnotify-bin. В Fedora и Arch Linux - пакет libnotify. Также требуется наличие сервера уведомлений. При запуске nohang от рута уведомления рассылаются всем залогиненным пользователям. See also wiki.archlinux.org/index.php/Desktop_notifications Valid values are True and False. gui_notifications = False Additional options for notify-send. See `notify-send --help` and read `man notify-send` For example: notify_options = -u "critical" notify_options = -t "20000" -i "dialog-warning" notify_options = Переменая окружения $DISPLAY, передаваемая notify-send при запуске nohang с uid = 0. Должен совпадать с выводом $ echo $DISPLAY root_display = :0 Enable GUI notifications about the low level of available memory. Для работы опции должны быть включены десктопные уведомления. Valid values are True and False. gui_low_memory_warnings = False Минимальное время между отправками уведомлений в секундах. Valid values are floating-point numbers from the range [1; 300]. min_time_between_warnings = 20 Если значения MemAvailable и SwapFree одновременно будут ниже соотвестствующих значений, то будут отправлены уведомления. Can be specified in % (percent) and M (MiB). Valid values are floating-point numbers from the range [0; 100] %. mem_min_warnings = 20 % swap_min_warnings = 20 % Если доля zram в памяти превысит значение zram_max_warnings, то будут отправляться уведомления с минимальным периодом равным min_time_between_warnings. zram_max_warnings = 40 % ##################################################################### 7. Preventing the slowing down of the program mlockall() lock ... all of the calling process's virtual address space into RAM, preventing that memory from being paged to the swap area. - `man mlockall` It is disabled by default because the value mlockall = True in Fedora 28 causes the process to increase memory consumption by 200 MiB. On Debian 8 and 9 there is no such problem. mlockall = False Установка отрицательных значений niceness и oom_score_adj требует наличия root прав. Установка отрицательного niceness повышает приоритет процесса. Valid values are integers from the range [-20; 19]. niceness = -15 Set oom_score_adj for the nohang process. Valid values are integers from the range [-1000; 1000]. Setting the values to -1000 will prohibit suicide. oom_score_adj = -100 Read `man ionice` to understand the following parameters. Setting the True value requires the root privileges. realtime_ionice = True 'For realtime and best-effort, 0-7 are valid data (priority levels), and 0 represents the highest priority level.' - `man ionice` Valid values are integers from the range [0; 7]. realtime_ionice_classdata = 5 ##################################################################### 8. Output verbosity Display the configuration when the program starts. Valid values are True and False. print_config = False Print memory check results or not print. Valid values are True and False. print_mem_check_results = False Print sleep periods between memory checks or not print. Valid values are True and False. print_sleep_periods = False