[PATCH v3 0/4] implement vcpu preempted check

Pan Xinhui xinhui.pan at linux.vnet.ibm.com
Thu Jul 21 21:45:10 AEST 2016

change from v2:
	no code change, fix typos, update some comments

change from v1:
	a simplier definition of default vcpu_is_preempted
	skip mahcine type check on ppc, and add config. remove dedicated macro.
	add one patch to drop overload of rwsem_spin_on_owner and mutex_spin_on_owner. 
	add more comments
	thanks boqun and Peter's suggestion.

This patch set aims to fix lock holder preemption issues.

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

before patch:
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

after patch:
 9.99%  sched-messaging  [kernel.vmlinux]  [k] mutex_unlock
 5.28%  sched-messaging  [unknown]         [H] 0xc0000000000768e0
 4.27%  sched-messaging  [kernel.vmlinux]  [k] __copy_tofrom_user_power7
 3.77%  sched-messaging  [kernel.vmlinux]  [k] copypage_power7
 3.24%  sched-messaging  [kernel.vmlinux]  [k] _raw_write_lock_irq
 3.02%  sched-messaging  [kernel.vmlinux]  [k] system_call
 2.69%  sched-messaging  [kernel.vmlinux]  [k] wait_consider_task

We introduce interface bool vcpu_is_preempted(int cpu) and use it in some spin
loops of osq_lock, rwsem_spin_on_owner and mutex_spin_on_owner.
These spin_on_onwer variant also cause rcu stall before we apply this patch set

Pan Xinhui (4):
  kernel/sched: introduce vcpu preempted check interface
  powerpc/spinlock: support vcpu preempted check
  locking/osq: Drop the overhead of osq_lock()
  kernel/locking: Drop the overhead of {mutex,rwsem}_spin_on_owner

 arch/powerpc/include/asm/spinlock.h | 18 ++++++++++++++++++
 include/linux/sched.h               | 12 ++++++++++++
 kernel/locking/mutex.c              | 15 +++++++++++++--
 kernel/locking/osq_lock.c           | 10 +++++++++-
 kernel/locking/rwsem-xadd.c         | 16 +++++++++++++---
 5 files changed, 65 insertions(+), 6 deletions(-)


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