linux.git/kernel/sched/core.c, branch v3.6-rc2

Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2012-08-03T17:58:13+00:00

Pull scheduler fixes from Ingo Molnar:
 "Fixes and two late cleanups"

* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched/cleanups: Add load balance cpumask pointer to 'struct lb_env'
  sched: Fix comment about PREEMPT_ACTIVE bit location
  sched: Fix minor code style issues
  sched: Use task_rq_unlock() in __sched_setscheduler()
  sched/numa: Add SD_PERFER_SIBLING to CPU domain

Merge branch 'perf-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2012-07-31T22:34:13+00:00

Pull perf updates from Ingo Molnar:
 "The biggest changes are Intel Nehalem-EX PMU uncore support, uprobes
  updates/cleanups/fixes from Oleg and diverse tooling updates (mostly
  fixes) now that Arnaldo is back from vacation."

* 'perf-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (40 commits)
  uprobes: __replace_page() needs munlock_vma_page()
  uprobes: Rename vma_address() and make it return "unsigned long"
  uprobes: Fix register_for_each_vma()->vma_address() check
  uprobes: Introduce vaddr_to_offset(vma, vaddr)
  uprobes: Teach build_probe_list() to consider the range
  uprobes: Remove insert_vm_struct()->uprobe_mmap()
  uprobes: Remove copy_vma()->uprobe_mmap()
  uprobes: Fix overflow in vma_address()/find_active_uprobe()
  uprobes: Suppress uprobe_munmap() from mmput()
  uprobes: Uprobe_mmap/munmap needs list_for_each_entry_safe()
  uprobes: Clean up and document write_opcode()->lock_page(old_page)
  uprobes: Kill write_opcode()->lock_page(new_page)
  uprobes: __replace_page() should not use page_address_in_vma()
  uprobes: Don't recheck vma/f_mapping in write_opcode()
  perf/x86: Fix missing struct before structure name
  perf/x86: Fix format definition of SNB-EP uncore QPI box
  perf/x86: Make bitfield unsigned
  perf/x86: Fix LLC-* and node-* events on Intel SandyBridge
  perf/x86: Add Intel Nehalem-EX uncore support
  perf/x86: Fix typo in format definition of uncore PCU filter
  ...

sched: Deliver sched_switch events to the current task

2012-07-26T10:23:10+00:00

Otherwise they can't be filtered for a defined task:

  perf record -e sched:sched_switch ./foo

This command doesn't report any events without this patch.

I think it isn't a security concern if someone knows who will
be executed next - this can already be observed by polling /proc
state. By default perf is disabled for non-root users in any case.

I need these events for profiling sleep times.  sched_switch is used for
getting callchains and sched_stat_* is used for getting time periods.
These events are combined in user space, then it can be analyzed by
perf tools.

Signed-off-by: Andrew Vagin 
Signed-off-by: Peter Zijlstra 
Cc: Steven Rostedt 
Cc: Arun Sharma 
Link: http://lkml.kernel.org/r/1342088069-1005148-1-git-send-email-avagin@openvz.org
Signed-off-by: Ingo Molnar

sched: Use task_rq_unlock() in __sched_setscheduler()

2012-07-26T09:46:59+00:00

It seems there's no specific reason to open-code it.  I guess
commit 0122ec5b02f76 ("sched: Add p->pi_lock to task_rq_lock()")
simply missed it.  Let's be consistent with others.

Signed-off-by: Namhyung Kim 
Signed-off-by: Peter Zijlstra 
Link: http://lkml.kernel.org/r/1341647342-6742-1-git-send-email-namhyung@kernel.org
Signed-off-by: Ingo Molnar

sched: Fix race in task_group()

2012-07-24T11:58:20+00:00

Stefan reported a crash on a kernel before a3e5d1091c1 ("sched:
Don't call task_group() too many times in set_task_rq()"), he
found the reason to be that the multiple task_group()
invocations in set_task_rq() returned different values.

Looking at all that I found a lack of serialization and plain
wrong comments.

The below tries to fix it using an extra pointer which is
updated under the appropriate scheduler locks. Its not pretty,
but I can't really see another way given how all the cgroup
stuff works.

Reported-and-tested-by: Stefan Bader 
Signed-off-by: Peter Zijlstra 
Link: http://lkml.kernel.org/r/1340364965.18025.71.camel@twins
Signed-off-by: Ingo Molnar

sched: Improve scalability via 'CPU buddies', which withstand random perturbations

2012-07-24T11:53:34+00:00

Traversing an entire package is not only expensive, it also leads to tasks
bouncing all over a partially idle and possible quite large package.  Fix
that up by assigning a 'buddy' CPU to try to motivate.  Each buddy may try
to motivate that one other CPU, if it's busy, tough, it may then try its
SMT sibling, but that's all this optimization is allowed to cost.

Sibling cache buddies are cross-wired to prevent bouncing.

4 socket 40 core + SMT Westmere box, single 30 sec tbench runs, higher is better:

 clients     1       2       4        8       16       32       64      128
 ..........................................................................
 pre        30      41     118      645     3769     6214    12233    14312
 post      299     603    1211     2418     4697     6847    11606    14557

A nice increase in performance.

Signed-off-by: Mike Galbraith 
Signed-off-by: Peter Zijlstra 
Cc: Linus Torvalds 
Cc: Andrew Morton 
Cc: Thomas Gleixner 
Link: http://lkml.kernel.org/r/1339471112.7352.32.camel@marge.simpson.net
Signed-off-by: Ingo Molnar

cpusets, hotplug: Restructure functions that are invoked during hotplug

2012-07-24T11:53:22+00:00

Separate out the cpuset related handling for CPU/Memory online/offline.
This also helps us exploit the most obvious and basic level of optimization
that any notification mechanism (CPU/Mem online/offline) has to offer us:
"We *know* why we have been invoked. So stop pretending that we are lost,
and do only the necessary amount of processing!".

And while at it, rename scan_for_empty_cpusets() to
scan_cpusets_upon_hotplug(), which is more appropriate considering how
it is restructured.

Signed-off-by: Srivatsa S. Bhat 
Signed-off-by: Peter Zijlstra 
Cc: Linus Torvalds 
Cc: Andrew Morton 
Cc: Thomas Gleixner 
Link: http://lkml.kernel.org/r/20120524141650.3692.48637.stgit@srivatsabhat.in.ibm.com
Signed-off-by: Ingo Molnar

CPU hotplug, cpusets, suspend: Don't modify cpusets during suspend/resume

2012-07-24T11:53:14+00:00

In the event of CPU hotplug, the kernel modifies the cpusets' cpus_allowed
masks as and when necessary to ensure that the tasks belonging to the cpusets
have some place (online CPUs) to run on. And regular CPU hotplug is
destructive in the sense that the kernel doesn't remember the original cpuset
configurations set by the user, across hotplug operations.

However, suspend/resume (which uses CPU hotplug) is a special case in which
the kernel has the responsibility to restore the system (during resume), to
exactly the same state it was in before suspend.

In order to achieve that, do the following:

1. Don't modify cpusets during suspend/resume. At all.
   In particular, don't move the tasks from one cpuset to another, and
   don't modify any cpuset's cpus_allowed mask. So, simply ignore cpusets
   during the CPU hotplug operations that are carried out in the
   suspend/resume path.

2. However, cpusets and sched domains are related. We just want to avoid
   altering cpusets alone. So, to keep the sched domains updated, build
   a single sched domain (containing all active cpus) during each of the
   CPU hotplug operations carried out in s/r path, effectively ignoring
   the cpusets' cpus_allowed masks.

   (Since userspace is frozen while doing all this, it will go unnoticed.)

3. During the last CPU online operation during resume, build the sched
   domains by looking up the (unaltered) cpusets' cpus_allowed masks.
   That will bring back the system to the same original state as it was in
   before suspend.

Ultimately, this will not only solve the cpuset problem related to suspend
resume (ie., restores the cpusets to exactly what it was before suspend, by
not touching it at all) but also speeds up suspend/resume because we avoid
running cpuset update code for every CPU being offlined/onlined.

Signed-off-by: Srivatsa S. Bhat 
Signed-off-by: Peter Zijlstra 
Cc: Linus Torvalds 
Cc: Andrew Morton 
Cc: Thomas Gleixner 
Link: http://lkml.kernel.org/r/20120524141611.3692.20155.stgit@srivatsabhat.in.ibm.com
Signed-off-by: Ingo Molnar

Merge branches 'core-urgent-for-linus', 'perf-urgent-for-linus' and 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2012-07-14T18:16:24+00:00

Pull RCU, perf, and scheduler fixes from Ingo Molnar.

The RCU fix is a revert for an optimization that could cause deadlocks.

One of the scheduler commits (164c33c6adee "sched: Fix fork() error path
to not crash") is correct but not complete (some architectures like Tile
are not covered yet) - the resulting additional fixes are still WIP and
Ingo did not want to delay these pending fixes.  See this thread on
lkml:

  [PATCH] fork: fix error handling in dup_task()

The perf fixes are just trivial oneliners.

* 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  Revert "rcu: Move PREEMPT_RCU preemption to switch_to() invocation"

* 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  perf kvm: Fix segfault with report and mixed guestmount use
  perf kvm: Fix regression with guest machine creation
  perf script: Fix format regression due to libtraceevent merge
  ring-buffer: Fix accounting of entries when removing pages
  ring-buffer: Fix crash due to uninitialized new_pages list head

* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  MAINTAINERS/sched: Update scheduler file pattern
  sched/nohz: Rewrite and fix load-avg computation -- again
  sched: Fix fork() error path to not crash

sched/nohz: Rewrite and fix load-avg computation -- again

2012-07-05T18:58:13+00:00

Thanks to Charles Wang for spotting the defects in the current code:

 - If we go idle during the sample window -- after sampling, we get a
   negative bias because we can negate our own sample.

 - If we wake up during the sample window we get a positive bias
   because we push the sample to a known active period.

So rewrite the entire nohz load-avg muck once again, now adding
copious documentation to the code.

Reported-and-tested-by: Doug Smythies 
Reported-and-tested-by: Charles Wang 
Signed-off-by: Peter Zijlstra 
Cc: Linus Torvalds 
Cc: Andrew Morton 
Cc: stable@kernel.org
Link: http://lkml.kernel.org/r/1340373782.18025.74.camel@twins
[ minor edits ]
Signed-off-by: Ingo Molnar