smp系统上的Posix线程

Question

I have developed a C app in linux sytem with 12 posix threads in it.It is a multicore system. After reading i found that kernel knows only my process and it will be unaware of threads(posix library will take care). In this case does my 12 threads will be using only onecore in which the process is sceduled or my threads can run in all available cores ? Does Posix library can schedule threads to other cores ?

Answer 1

Historically, there have been quite a few libraries which implemented POSIX-threads-like functionality. LinuxThreads came with glibc, but had severe conformance issues due to limitations of earlier kernels (such as a thread-specific current directory and umask). It could actually run multiple threads in the same process on different CPUs at the same time (people didn't speak of cores back then). FSU Threads had better POSIX conformance (even in the area of PI scheduling, if I recall correctly), but was restricted to one CPU per process. Many thread libraries also experimented with an n:m scheme, where a larger number of user space threads was executed on a small number of kernel-scheduled threads (which could run in parallel on different CPUs).

For Linux and C/C++, this pretty much stopped when NPTL was added to glibc and more and more tightly integrated with the rest of the library. NPTL has a 1:1 model: each user space thread is visible to the kernel and can run in parallel, as long sufficient hardware resources are available.