[RFC v1 PATCH 0/7] CFS Hard limits - v1

From: Bharata B Rao
Date: Tue Aug 25 2009 - 05:47:38 EST


RFC on Hard limits feature for CFS group scheduler was posted earlier at
http://lkml.org/lkml/2009/6/4/24. This is the next RFC post with patches.

During the previous post, the need for hard limits feature was acknowledged.
Also it was mentioned that guarantees would also be desirable. This post
just addresses the limits part and there is no intention to address the
guarantees problem with this patchset.

This patchset has seen some very light testing and I believe that there will
be bugs in it. However if you feel brave enough, this patchset could be tried
on 2.6.31-rc7!

Features TODO
- Runtime borrowing isn't implemented yet, plan to add it in subsequent posts.
- Bandwidth inheritence support (long term, not under consideration currently)
- This implementation doesn't work for user group scheduler. Since user group
scheduler will eventually go away, I don't plan to work on this.

Implementation TODO
- This patchset has seen very minimal testing. I need to test this under
more test scenarios.
- I have been testing this on a 8 CPU box. Need to see how this behaves
on a bigger box.
- Need to run performance tests and regression tests for benchmarks on bigger
- It is possible to share some of the bandwidth handling code with RT, but
the intention of this post is to show the changes associated with hard limits.
Hence the sharing/cleanup will be done down the line when this patchset
itself becomes more accepatable.
- When a dequeued entity is enqueued back, I don't change its vruntime. The
entity might get undue advantage due to its old (lower) vruntime. Need to
address this.

This set has the following patches:

1/7 sched: Rename sched_rt_period_mask() and use it in CFS also
2/7 sched: Maintain aggregated tasks count in cfs_rq at each hierarchy level
3/7 sched: Bandwidth initialization for fair task groups
4/7 sched: Enforce hard limits by throttling
5/7 sched: Unthrottle the throttled tasks
6/7 sched: Add throttle time statistics to /proc/sched_debug
7/7 sched: Hard limits documentation

Documentation/scheduler/sched-cfs-hard-limits.txt | 52 +++
include/linux/sched.h | 7
init/Kconfig | 13
kernel/sched.c | 346 +++++++++++++++++++-
kernel/sched_debug.c | 21 +
kernel/sched_fair.c | 268 +++++++++++++++
kernel/sched_rt.c | 19 -
7 files changed, 703 insertions(+), 23 deletions(-)

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