[patch/backport] CFS scheduler, -v22, for v2.6.23-rc8, v2.6.22.8,v2.6.21.7, v2.6.20.20

From: Ingo Molnar
Date: Wed Sep 26 2007 - 07:14:23 EST

By popular demand, here is release -v22 of the CFS scheduler. It is a
full backport of the latest & greatest sched-devel.git code to
v2.6.23-rc8, v2.6.22.8, v2.6.21.7 and v2.6.20.20. The patches can be
downloaded from the usual place:


This is the first time the development version of the scheduler has been
fed back into the stable backport series, so there's many changes since

15 files changed, 1103 insertions(+), 840 deletions(-)

Even if CFS v20.5 worked well for you, please try this release too, with
a good focus on interactivity testing - because, unless some major
showstopper is found, this codebase is intended for a v2.6.24 upstream

( Even a quick, subjective report of: "checked this patch, it didnt
crash and it feels like v20.5" or "laggier than v20.5" or "feels
better than v20.5" is useful to us and enables us to judge the general
direction of interactivity. )

The changes in v22 consist of lots of mostly small enhancements,
speedups, interactivity improvements, debug enhancements and tidy-ups -
many of which can be user-visible. (These enhancements have been
contributed by many people - see the changelog below and the git tree
for detailed credits.)

The biggest individual new feature is per UID group scheduling, written
by Srivatsa Vaddagiri, which can be enabled via the
CONFIG_FAIR_USER_SCHED=y .config option. With this feature enabled, each
user gets a fair share of the CPU time, regardless of how many tasks
each user is running.

For example, it took me 0.1 seconds to log in over ssh as root on a
testbox that was running a kernel with per UID group scheduling enabled:

$ time ssh root@testbox /bin/true

real 0m0.125s
user 0m0.013s
sys 0m0.011s

Which testbox had a system load of 1000.17 at this time, due to a rogue
runaway workload of one thousand (!) non-reniced infinite loops:

top - 14:34:05 up 30 min, 3 users, load average: 1000.17, 839.23, 444.57
Tasks: 1131 total, 1002 running, 129 sleeping, 0 stopped, 0 zombie
Cpu(s): 30.8%us, 0.2%sy, 0.0%ni, 68.2%id, 0.8%wa, 0.0%hi, 0.0%si
Mem: 2048992k total, 157688k used, 1891304k free, 18308k buffers
Swap: 4096564k total, 0k used, 4096564k free, 25464k cached

3633 root 20 0 2892 1576 724 R 7 0.1 0:00.06 top
2427 mingo 20 0 1576 244 196 R 2 0.0 0:01.14 loop
2429 mingo 20 0 1576 244 196 R 2 0.0 0:01.14 loop

To the root user, the box was fully usable an interactivity was
excellent - i was easily able to kill off those runaway tasks.

( The /proc/root_user_cpu_share tunable also allows the root uid to have
higher weight than other uids. Unit of the tunable is 0.1%, a weight
of 100% is 1024, the default weight of the root uid is 200%. )

See the detailed shortlog below for a description of the other changes,
or pull the sched-devel.git tree for all the 83 commits:

git-pull git://git.kernel.org/pub/scm/linux/kernel/git/mingo/linux-2.6-sched-devel.git

Also, as usual, any sort of feedback, bugreport, fix and suggestion is
more than welcome!


Dmitry Adamushko (9):
sched: clean up struct load_stat
sched: clean up schedstat block in dequeue_entity()
sched: sched_setscheduler() fix
sched: add set_curr_task() calls
sched: do not keep current in the tree and get rid of sched_entity::fair_key
sched: optimize task_new_fair()
sched: simplify sched_class::yield_task()
sched: rework enqueue/dequeue_entity() to get rid of set_curr_task()
sched: yield fix

Hiroshi Shimamoto (1):
sched: clean up sched_fork()

Matthias Kaehlcke (1):
sched: use list_for_each_entry_safe() in __wake_up_common()

Mike Galbraith (2):
sched: fix SMP migration latencies
sched: fix formatting of /proc/sched_debug

Peter Zijlstra (12):
sched: simplify SCHED_FEAT_* code
sched: new task placement for vruntime
sched: simplify adaptive latency
sched: clean up new task placement
sched: add tree based averages
sched: handle vruntime overflow
sched: better min_vruntime tracking
sched: add vslice
sched debug: check spread
sched: max_vruntime() simplification
sched: clean up min_vruntime use
sched: speed up and simplify vslice calculations

S.Caglar Onur (1):
sched debug: BKL usage statistics, fix

Srivatsa Vaddagiri (12):
sched: group-scheduler core
sched: revert recent removal of set_curr_task()
sched: fix minor bug in yield
sched: print nr_running and load in /proc/sched_debug
sched: print &rq->cfs stats
sched: clean up code under CONFIG_FAIR_GROUP_SCHED
sched: add fair-user scheduler
sched: group scheduler wakeup latency fix
sched: group scheduler SMP migration fix
sched: group scheduler, fix coding style issues
sched: group scheduler, fix bloat
sched: group scheduler, fix latency

Ingo Molnar (44):
sched: fix new-task method
sched: resched task in task_new_fair()
sched: small sched_debug cleanup
sched: debug: track maximum 'slice'
sched: uniform tunings
sched: use constants if !CONFIG_SCHED_DEBUG
sched: remove stat_gran
sched: remove precise CPU load
sched: remove precise CPU load calculations #2
sched: track cfs_rq->curr on !group-scheduling too
sched: cleanup: simplify cfs_rq_curr() methods
sched: uninline __enqueue_entity()/__dequeue_entity()
sched: speed up update_load_add/_sub()
sched: clean up calc_weighted()
sched: introduce se->vruntime
sched: move sched_feat() definitions
sched: optimize vruntime based scheduling
sched: simplify check_preempt() methods
sched: wakeup granularity fix
sched: add se->vruntime debugging
sched: add more vruntime statistics
sched: debug: update exec_clock only when SCHED_DEBUG
sched: remove wait_runtime limit
sched: remove wait_runtime fields and features
sched: x86: allow single-depth wchan output
sched: fix delay accounting performance regression
sched: prettify /proc/sched_debug output
sched: enhance debug output
sched: kernel/sched_fair.c whitespace cleanups
sched: fair-group sched, cleanups
sched: enable CONFIG_FAIR_GROUP_SCHED=y by default
sched debug: BKL usage statistics
sched: remove unneeded tunables
sched debug: print settings
sched debug: more width for parameter printouts
sched: entity_key() fix
sched: remove condition from set_task_cpu()
sched: remove last_min_vruntime effect
sched: undo some of the recent changes
sched: fix place_entity()
sched: fix sched_fork()
sched: remove set_leftmost()
sched: clean up schedstats, cnt -> count
sched: cleanup, remove stale comment

arch/i386/Kconfig | 11
fs/proc/base.c | 2
include/linux/sched.h | 56 ++-
init/Kconfig | 21 +
kernel/delayacct.c | 2
kernel/sched.c | 577 ++++++++++++++++++++++++-------------
kernel/sched_debug.c | 246 ++++++++++------
kernel/sched_fair.c | 733 ++++++++++++++++++------------------------------
kernel/sched_idletask.c | 5
kernel/sched_rt.c | 12
kernel/sched_stats.h | 28 -
kernel/sysctl.c | 31 --
kernel/user.c | 43 ++
13 files changed, 963 insertions(+), 804 deletions(-)
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