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 libpthread; this is straightforward. In the application's makefile(s), change the -pthread compiler switch or -lc_r link option to -lpthread and relink. Alternatively, you can use /etc/libmap.conf to map libc_r to libpthread (see libmap.conf(5)).
Following is an incomplete general list of tasks:
| Module | Task | Responsible | Last updated | Status |
|---|---|---|---|---|
| libpthread | Write kse(2) man page documenting new system calls. | &a.archie; | 10 September 2002 | &status.done; |
| libpthread | Repo-copy the libpthread library from libc_r. | cvs meister | 16 September 2002 | &status.done; |
| libpthread | Use KSE to schedule processes. | &a.mini; | 30 October 2002 | &status.done; |
| libpthread | Schedule an idle context when appropriate. | &a.mini; | 2 November 2002 | &status.done; |
| libpthread | Deliver signals to threads. | &a.deischen; &a.davidxu; | 28 June 2003 | &status.done; |
| libpthread | Locking for SMP. | &a.deischen; | 3 May 2003 | &status.done; |
| kernel | Locking for SMP. | &a.davidxu; | 3 May 2003 | &status.done; |
| libpthread | Launch multiple KSEs (one per CPU). | &a.davidxu; | 3 May 2003 | &status.done; |
| libpthread, kernel | Implement alpha machine-dependent functions. | &a.marcel; | 30 Aug 2003 | &status.wip; |
| libpthread, kernel | Implement amd64 machine-dependent functions. | &a.davidxu; &a.deischen; | 30 Aug 2003 | &status.done; |
| libpthread, kernel | Implement i386 machine-dependent functions. | &a.davidxu; &a.deischen; | 30 Aug 2003 | &status.done; |
| libpthread, kernel | Implement ia64 machine-dependent functions. | &a.marcel; | 30 Aug 2003 | &status.done; |
| libpthread, kernel | Implement sparc64 machine-dependent functions. | &a.jake; | 30 Aug 2003 | &status.wip; |
| kernel | Implement KSE-specific signaling. | &a.davidxu; | 28 June 2003 | &status.done; |
| libpthread | Implement scope system threads. | &a.deischen; | 3 May 2003 | &status.done; |
| kernel | Efficient scope system threads (no upcalls when they block). | &a.davidxu; | 30 Aug 2003 | &status.done; |