Kernel Scheduler Entities (KSE), is a kernel-supported threading system similar in design to Scheduler Activations [Anderson, et. al.]. It strikes a balance between user-level (1:N) and kernel-level (1:1) threading models, giving most of the advantages of both, and few of the disadvantages of either.
There are two halves of this project: kernel support and user support. The kernel support consists of modifications to the FreeBSD scheduler; The user half is a POSIX threads implementation which takes advantage of the extra facilities the kernel provides.
The goal is to replace the current user threading system provided by the libc_r library, and the -pthread gcc option, with a new libpthread library which will be linked with the -lpthread gcc option.
All KSE development is being done in 5.0-CURRENT. No special kernel configuration options are required to build a kernel with the KSE-related changes (the changes are inextricable from the FreeBSD scheduler).
In order to use KSE in an application, you need to link it against libpthreads, which is not built by default. To build and install it on your system, either run make all install from /usr/src/lib/libpthread (if you have sources installed on your system), or check out the libpthread and libc modules from CVS. You don't need to rebuild libc, but the libpthread makefiles refer to parts of the libc sources.
Linking an application against libpthread is straightforward. In its makefiles, change the -pthread option to -lpthread and relink. Alternatively, you can copy libpthread.so on top of libc_r.so, but this is not recommended until libpthread.so becomes a bit more stable.
Following is an incomplete general list of tasks:
| Module | Task | Responsible | Last updated | Status |
|---|---|---|---|---|
| libpthread | Write kse(2) man page documenting new system calls. | Archie Cobbs | 10 September 2002 | Done |
| libpthread | Repo-copy the libpthread library from libc_r. | cvs meister | 16 September 2002 | Done |
| libpthread | Use KSE to schedule processes. | Jonathan Mini | 30 October 2002 | Done |
| libpthread | Schedule an idle context when appropriate. | Jonathan Mini | 2 November 2002 | Done |
| libpthread | Deliver signals to threads. | Daniel Eischen David Xu | 28 June 2003 | Done |
| libpthread | Locking for SMP. | Daniel Eischen | 3 May 2003 | Done |
| kernel | Locking for SMP. | David Xu | 3 May 2003 | Done |
| libpthread | Launch multiple KSEs (one per CPU). | David Xu | 3 May 2003 | Done |
| libpthread | Implement machine-dependent functions for non-x86 platforms. | Marcel Moolenaar | 28 June 2003 | In progress |
| kernel | Implement machine-dependent functions for non-x86 platforms. | Marcel Moolenaar | 28 June 2003 | In progress |
| Port NetBSD's liblwp to FreeBSD/KSE. | 2 November 2002 | Not Started | ||
| kernel | Implement KSE-specific signaling. | David Xu | 28 June 2003 | Done |
| libpthread | Implement scope system threads. | Daniel Eischen | 3 May 2003 | Done |
| kernel | Efficient scope system threads (no upcalls when they block). | David Xu | 3 May 2003 | In progress |