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[PATCH 0/2] implement vcpu preempted check

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  [PATCH 0/2] implement vcpu preempted check Pan Xinhui <xinhui.pan@linux.vnet.ibm.com> - 2016-06-26 08:50 +0200

#1431350 — [PATCH 0/2] implement vcpu preempted check

This is to fix some bad issues on an over-commited 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 (1):
  locking/osq: Drop the overload of osq_lock()

pan xinhui (1):
  kernel/sched: introduce vcpu preempted interface

 include/linux/sched.h     | 34 ++++++++++++++++++++++++++++++++++
 kernel/locking/osq_lock.c | 18 +++++++++++++++---
 2 files changed, 49 insertions(+), 3 deletions(-)

-- 
2.4.11

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