[PATCH 0/3] implement vcpu preempted check

[Pan Xinhui <xinhui.pan@linux.vnet.ibm.com>]

This is to fix some bad issues on an over-committed guest.

test-caes:
perf record -a perf bench sched messaging -g 400 -p && perf report

18.09%  sched-messaging  [kernel.vmlinux]  [k] osq_lock
12.28%  sched-messaging  [kernel.vmlinux]  [k] rwsem_spin_on_owner
 5.27%  sched-messaging  [kernel.vmlinux]  [k] mutex_unlock
 3.89%  sched-messaging  [kernel.vmlinux]  [k] wait_consider_task
 3.64%  sched-messaging  [kernel.vmlinux]  [k] _raw_write_lock_irq
 3.41%  sched-messaging  [kernel.vmlinux]  [k] mutex_spin_on_owner.is
 2.49%  sched-messaging  [kernel.vmlinux]  [k] system_call

osq takes a long time with preemption disabled which is really bad.

This is because vCPU A hold the osq lock and yield out, vCPU B wait
per_cpu node->locked to be set. IOW, vCPU B wait vCPU A to run and
unlock the osq lock. Even there is need_resched(), it did not help on
such scenario.

we may also need fix other XXX_spin_on_owner later based on this patch set.
these spin_on_onwer variant cause rcu stall.

Pan Xinhui (3):
  powerpc/spinlock: support vcpu preempted check
  locking/osq: Drop the overload of osq_lock()
  kernel/sched: introduce vcpu preempted check interface

 arch/powerpc/include/asm/lppaca.h   |  6 ++++++
 arch/powerpc/include/asm/spinlock.h | 15 +++++++++++++++
 include/linux/sched.h               |  9 +++++++++
 kernel/locking/osq_lock.c           | 16 +++++++++++++++-
 4 files changed, 45 insertions(+), 1 deletion(-)

-- 
2.4.11