[0/7] scheduler tinification

Message ID 20170529210302.26868-1-nicolas.pitre@linaro.org
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  • scheduler tinification
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Nicolas Pitre May 29, 2017, 9:02 p.m.
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

And for the record, my Fedora workstation still boots and apparently runs
fine with those patches activated. I didn't test it at length though.

A significant part of the remaining code is support for various system calls
that could be automatically removed when user space doesn't use them but that
is a topic for another day.

diffstat for this series:

 include/linux/init_task.h      |  15 +-
 include/linux/rtmutex.h        |  69 ++++
 include/linux/sched.h          |   4 +
 include/linux/sched/deadline.h |   2 +-
 include/linux/sched/rt.h       |   4 +-
 init/Kconfig                   |  23 +-
 kernel/locking/Makefile        |   2 +
 kernel/locking/rtmutex.c       |   9 +
 kernel/sched/Makefile          |   7 +-
 kernel/sched/core.c            | 777 +++++------------------------------
 kernel/sched/deadline.c        | 336 +++++++++++++++
 kernel/sched/debug.c           |   6 +
 kernel/sched/rt.c              | 320 ++++++++++++++-
 kernel/sched/sched.h           |  35 +-
 kernel/sched/stop_task.c       |   6 +
 kernel/sched/topology.c        |   6 +
 kernel/sysctl.c                |   4 +-
 kernel/time/posix-cpu-timers.c |   6 +-
 lib/Kconfig.debug              |   2 +-
 19 files changed, 930 insertions(+), 703 deletions(-)

Comments

Peter Zijlstra May 30, 2017, 8:32 a.m. | #1
On Mon, May 29, 2017 at 05:02:55PM -0400, Nicolas Pitre wrote:
> 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.


Not happy with this. We already have too many CONFIG_ knobs, I really
don't want more.