Linux show process threads

4 commands to check thread count per process (threads vs processes) in Linux

Table of Contents

In Linux, some processes are divided into pieces called threads. In one liner, threads are essentially just processes with a shared address space on Linux. In this article we will get some brief overview on threads and processes, also some examples to show threads per process, check thread count per process, check number of threads allowed, count threads and some more related topics.

Threads vs Processes

• A thread is very similar to a process, it has an identifier (TID, or thread ID), and the kernel schedules and runs threads just like processes.
• However, unlike separate processes, which usually do not share system resources such as memory and I/O connections with other processes, all threads inside a single process share their system resources and some memory.
• A process with one thread is single-threaded , and a process with more than one thread is multithreaded .
• All processes start out single-threaded . This starting thread is usually called the main thread. The main thread may then start new threads in order for the process to become multithreaded, similar to the way a process can call fork() to start a new process.
• The primary advantage of a multithreaded process is that when the process has a lot to do, threads can run simultaneously on multiple processors, potentially speeding up computation.
• Although you can also achieve simultaneous computation with multiple processes, threads start faster than processes, and it is often easier and/or more efficient for threads to intercommunicate using their shared memory than it is for processes to communicate over a channel such as a network connection or a pipe.

Show threads per process

1. Using PID task

You can count threads with the list of available sub directories inside /proc/

/task/ . The count of total available sub-directories inside this part is directly proportional to the thread count per process for the provided PID.

For example to check java thread count, I have a Java process for which you can see I have multiple sub-directories so it means this is a multi threaded process. using ls command under this path you can show threads per process for java

But then again I have another process for which as you can see I have single sub-directory hence we know this is a single thread process

2. Using ps command

You can also use » ps » command to show threads per process. With » ps » we can list LWP (Light Weight process) which depicts Thread ID of the respective process and NWLP (Number of Threads).

To show threads per process using ps command you can use below argument

3. Using pstree command

You can also use pstree to show threads per process. Here as you see java thread count and check number of threads for java process

4. Using top command

In top , by default we will not be able to see thread count per process. But when running top , it is possible to change which fields to display and add this column to print thread count per process can be added manually.

• Press f
• This will show a list of fields that top can display. The fields that are displayed in bold are the ones that top will display.
• Use the down arrow to navigate to «nTH» (Number of Threads).
• Press to select «nTH«
• Press ‘s‘ to sort on number of threads.
• Press ‘q‘ to display the data of threads count.

Next you should see a new column at the end of top command with number of thread (nTH) column to show threads per process

Check thread count per process

Next you can use the above explained commands to also check thread count per process by customising them a little bit.

1. Using PID status

To check thread count per process you can use below command. For example here java thread count is 59 threads in my Linux environment

While amsHelper process has single thread

2. Using ps command

We used ps command to show threads per process and count threads, we can also use » ps » command to get LWP and NLWP details, which when combined with » wc » we can count threads per process.

To check thread count per process for a particular PID for example to check java thread count:

Check number of threads allowed in Linux system?

Linux doesn’t have a separate threads per process limit, j ust a limit on the total number of processes on the system . This value controls the maximum number of threads that can be created using fork() . During initialization the kernel sets this value such that even if the maximum number of threads is created

To check number of threads which Linux system can allow

The minimum number of threads that can be written to threads-max is 20 .
The maximum value that can be written to threads-max is given by the constant FUTEX_TID_MASK (0x3fffffff) .
If a value outside of this range is written to threads-max an error EINVAL occurs.

The default value depends on memory size. You can use threads-max to check number of threads allowed in Linux. You can increase thread count per process limit like this:

There is also a limit on the number of processes (an hence threads) that a single user may create, see ulimit for details regarding these limits:

Here, the system is able to create 35,000 threads/processes in total and a single user can create 10000 number of processes.

The logic is very simple here every CPU can execute 1 process at a time, if there are 8 cores that means 8 to 10 processes at a time can be executed easily without any stress but if number of running or runnable threads per CPU increases drastically then there will be performance issue.

What is the maximum processes count allowed in Linux?

Verify the value for kernel.pid_max

Here I can execute 35,000 processes simultaneously in my system that can run in separate memory spaces.

To change the value of kernel.pid_max to 65534:

Lastly I hope the steps from the article to show threads per process, check thread count per process, check number of threads allowed on Linux was helpful. So, let me know your suggestions and feedback using the comment section.

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Linux show process threads

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How to view threads of a process on Linux

Threads are a popular programming abstraction for parallel execution on modern operating systems. When threads are forked inside a program for multiple flows of execution, these threads share certain resources (e.g., memory address space, open files) among themselves to minimize forking overhead and avoid expensive IPC (inter-process communication) channel. These properties make threads an efficient mechanism for concurrent execution.

In Linux, threads (also called Lightweight Processes (LWP)) created within a program will have the same «thread group ID» as the program’s PID. Each thread will then have its own thread ID (TID). To the Linux kernel’s scheduler, threads are nothing more than standard processes which happen to share certain resources. Classic command-line tools such as ps or top, which display process-level information by default, can be instructed to display thread-level information.

Here are several ways to show threads for a process on Linux:

Using the ps command

The «-T» option for the ps command enables thread views. The following command list all threads created by a process with

The «SID» column represents thread IDs, and «CMD» column shows thread names.

Using the top command

The top command can show a real-time view of individual threads. To enable thread views in the top output, invoke top with «-H» option. This will list all Linux threads. You can also toggle on or off thread view mode while top is running, by pressing ‘H’ key.

Note how in the example above the number of threads on the system is listed.

To restrict the top output to a particular process and check all threads running inside the process:

A more user-friendly way to view threads per process is via htop, an ncurses-based interactive process viewer. This program allows you to monitor individual threads in tree views.

To enable thread views in htop, launch htop, and press F2 to enter htop setup menu. Choose «Display option» under «Setup» column, and toggle on «Tree view» and «Show custom thread names» options. Presss F10 to exit the setup.

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Как посмотреть потоки процесса в Linux

Потоки это популярная программная абстракция для параллельного выполнения в современных операционных системах. Когда программа делиться на потоки для многопоточного выполнения, ресурсы такие как адресное пространство оперативной памяти и открытые файлы делятся между потоками чтобы минимизировать накладные расходы и более эффективно использовать процессорное время. Эти возможности делают потоки эффективным механизмом много поточного выполнения.

Для планировщика ядра потоки ничем не отличаются от обычных процессов которые имеют общие ресурсы. Поэтому для просмотра потоков можно использовать такие классические инструменты командной строки как ps и top. В этой статье мы поговорим о том как посмотреть потоки процесса Linux.

Потоки процессов в Linux

Сразу необходимо разобраться в том что же такое процессы и потоки в linux и чем они отличаются от друг от друга. В Linux есть два способа наладить многопоточное выполнение какого-либо действия. Первый, когда процесс создает свои копии с помощью механизма fork и затем эти процессы взаимодействуют через сокеты или IPC. Тогда мы получаем отдельные процессы, каждый процесс имеет свои ресурсы и занимает память. Второй же способ подразумевает выделение потоков в рамках одного процесса. Все протоки одного процесса будут иметь один идентификатор группы потоков, а также уникальный идентификатор потока. Они будут иметь доступ ко всем ресурсам родительского процесса и занимать меньше памяти.

1. Утилита ps

В утилите ps показ потоков процесса включается опцией -T. Например вот такой командой можно посмотреть все потоки процесса с PID, например, для Chromium:

В колонке SPID отображается идентификатор потока, а в CMD его имя.

2. Утилита top

Команда top позволяет просматривать потоки в реальном времени. Для включения отображения потоков запустите top с опцией -H. Также можно включить или отключить показ потоков во время выполнения с помощью клавиши H:

Если вы хотите посмотреть только потоки нужного процесса выполните:

3. Утилита htop

Ну и как всегда под конец самое интересное. Самой удобной утилитой для просмотра потоков процесса я считаю команду htop. Это основный на ncurces интерактивный просмотрщик процессов. С помощью этой утилиты вы можете наблюдать за потоками в реальном времени в виде дерева.

Для того чтобы включить просмотр потоков в htop откройте программу, войдите в меню нажав клавишу F2, затем выберите Display Options, в разделе Setup. Теперь отметьте Three view и Show custom thread names. Все, можно нажимать F10 для сохранения настроек:

Теперь вы можете просматривать потоки в виде дерева отдельно для каждого процесса. Здесь снова отображаются потоки для браузера Chromium:

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