Many embedded systems don't need the full scheduler support. Most of the time, user space is tightly controlled and many of the scheduler facilities are simply unused.
This patch series makes it possible to configure out some parts of the scheduler such as the deadline and realtime scheduler classes. The saving in kernel footprint is non negligible. Small ARM kernel config before this series: text data bss dec hex filename 28623 3404 128 32155 7d9b kernel/sched/built-in.o With this series and dl and rt classes disabled: text data bss dec hex filename 20734 3334 40 24108 5e2c kernel/sched/built-in.o A significant part of the remaining code is support for various system calls that could be automatically removed when user space doesn't use it but that is a topic for another day. Changes from v1: - the deadline class is configurable independently from the realtime class - split of the PI futex code to make non-PI futexes available when RT is configured out - removal of many #ifdefs to keep the code more readable diffstat for this series: include/linux/futex.h | 7 +- include/linux/init_task.h | 15 +- include/linux/rtmutex.h | 69 + include/linux/sched.h | 4 + include/linux/sched/deadline.h | 8 +- include/linux/sched/rt.h | 10 +- init/Kconfig | 28 +- kernel/futex.c | 2829 ++++++++-------------------------- kernel/futex_pi.c | 1563 +++++++++++++++++++ kernel/locking/Makefile | 3 + kernel/locking/locktorture.c | 4 +- kernel/locking/rtmutex.c | 6 +- kernel/sched/Makefile | 7 +- kernel/sched/core.c | 759 +-------- kernel/sched/cpudeadline.h | 7 +- kernel/sched/deadline.c | 340 ++++ kernel/sched/debug.c | 6 + kernel/sched/rt.c | 315 +++- kernel/sched/sched.h | 88 +- kernel/sched/stop_task.c | 6 + kernel/sysctl.c | 4 +- kernel/time/posix-cpu-timers.c | 7 +- lib/Kconfig.debug | 2 +- 23 files changed, 3190 insertions(+), 2897 deletions(-)
