Wanpeng Li 89340d0935 Revert "locking/pvqspinlock: Don't wait if vCPU is preempted" ... This patch reverts commit 75437bb304 (locking/pvqspinlock: Don't wait if vCPU is preempted). A large performance regression was caused by this commit. on over-subscription scenarios. The test was run on a Xeon Skylake box, 2 sockets, 40 cores, 80 threads, with three VMs of 80 vCPUs each. The score of ebizzy -M is reduced from 13000-14000 records/s to 1700-1800 records/s: Host Guest score vanilla w/o kvm optimizations upstream 1700-1800 records/s vanilla w/o kvm optimizations revert 13000-14000 records/s vanilla w/ kvm optimizations upstream 4500-5000 records/s vanilla w/ kvm optimizations revert 14000-15500 records/s Exit from aggressive wait-early mechanism can result in premature yield and extra scheduling latency. Actually, only 6% of wait_early events are caused by vcpu_is_preempted() being true. However, when one vCPU voluntarily releases its vCPU, all the subsequently waiters in the queue will do the same and the cascading effect leads to bad performance. kvm optimizations: [1] commit d73eb57b80 (KVM: Boost vCPUs that are delivering interrupts) [2] commit 266e85a5ec (KVM: X86: Boost queue head vCPU to mitigate lock waiter preemption) Tested-by: loobinliu@tencent.com Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@kernel.org> Cc: Waiman Long <longman@redhat.com> Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Radim Krčmář <rkrcmar@redhat.com> Cc: loobinliu@tencent.com Cc: stable@vger.kernel.org Fixes: 75437bb304 (locking/pvqspinlock: Don't wait if vCPU is preempted) Signed-off-by: Wanpeng Li <wanpengli@tencent.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>		2019-09-25 10:22:37 +02:00
..
Makefile	…
lock_events.c	…
lock_events.h	…
lock_events_list.h	…
lockdep.c	Merge branch 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2019-09-16 16:49:55 -07:00
lockdep_internals.h	…
lockdep_proc.c	…
lockdep_states.h	…
locktorture.c	…
mcs_spinlock.h	…
mutex-debug.c	…
mutex-debug.h	…
mutex.c	mutex: Fix up mutex_waiter usage	2019-08-08 09:09:25 +02:00
mutex.h	mutex: Fix up mutex_waiter usage	2019-08-08 09:09:25 +02:00
osq_lock.c	…
percpu-rwsem.c	…
qrwlock.c	…
qspinlock.c	…
qspinlock_paravirt.h	Revert "locking/pvqspinlock: Don't wait if vCPU is preempted"	2019-09-25 10:22:37 +02:00
qspinlock_stat.h	…
rtmutex-debug.c	…
rtmutex-debug.h	…
rtmutex.c	…
rtmutex.h	…
rtmutex_common.h	…
rwsem.c	locking/rwsem: Check for operations on an uninitialized rwsem	2019-08-06 12:49:15 +02:00
rwsem.h	…
semaphore.c	…
spinlock.c	…
spinlock_debug.c	…
test-ww_mutex.c	…