Linux thread and POSIX are incompatible, and in the kernel, a thread is actually a process (but these threads are generated by clone). Therefore, there are many disadvantages, for example, we can see a multi-threaded program in some old systems (such as the versions earlier than redhat9 and the rhel as2 series), under top or PS or/proc, we can see a lot of Process Information items. This is because these threads exist in the kernel as processes. For details, see the Linux thread restrictions section in this article.
Nptl is the native POSIX thread library and is compatible with POSIX. This is a good thread solution today. nptl is used for both redhat9 and RHEL as3 and 4. Therefore, our pthread_create can run very well. In the top table, there is only one multi-threaded program, because it only has one process. For the specific advantages, see the article.
A good table in the article lists the versions of thread libraries in some mainstream Linux operating systems. If you want to check what thread library is used in Linux, it is also very simple. Just execute this command:
Getconf gnu_libthread_version
/Files/super119/linuxandnptlthread_882.mht.zip
