On 07/21/2016 01:45 PM, Pan Xinhui wrote:
> 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.
>
> test-case:
> 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(-)
>
Acked-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
for the full series. With my patch on top this really improves
some benchmarks for overcommitted KVM guests.
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