| Message ID | 20140615130153.940699466@chello.nl (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 06/15/2014 08:47 AM, Peter Zijlstra wrote: > When we detect a hypervisor (!paravirt, see later patches), revert to > a simple test-and-set lock to avoid the horrors of queue preemption. > > Signed-off-by: Peter Zijlstra<peterz@infradead.org> > --- > arch/x86/include/asm/qspinlock.h | 14 ++++++++++++++ > include/asm-generic/qspinlock.h | 7 +++++++ > kernel/locking/qspinlock.c | 3 +++ > 3 files changed, 24 insertions(+) > > --- a/arch/x86/include/asm/qspinlock.h > +++ b/arch/x86/include/asm/qspinlock.h > @@ -1,6 +1,7 @@ > #ifndef _ASM_X86_QSPINLOCK_H > #define _ASM_X86_QSPINLOCK_H > > +#include<asm/cpufeature.h> > #include<asm-generic/qspinlock_types.h> > > #if !defined(CONFIG_X86_OOSTORE)&& !defined(CONFIG_X86_PPRO_FENCE) > @@ -20,6 +21,19 @@ static inline void queue_spin_unlock(str > > #endif /* !CONFIG_X86_OOSTORE&& !CONFIG_X86_PPRO_FENCE */ > > +#define virt_queue_spin_lock virt_queue_spin_lock > + > +static inline bool virt_queue_spin_lock(struct qspinlock *lock) > +{ > + if (!static_cpu_has(X86_FEATURE_HYPERVISOR)) > + return false; > + > + while (atomic_cmpxchg(&lock->val, 0, _Q_LOCKED_VAL) != 0) > + cpu_relax(); > + > + return true; > +} > + > #include<asm-generic/qspinlock.h> > > #endif /* _ASM_X86_QSPINLOCK_H */ > --- a/include/asm-generic/qspinlock.h > +++ b/include/asm-generic/qspinlock.h > @@ -98,6 +98,13 @@ static __always_inline void queue_spin_u > } > #endif > > +#ifndef virt_queue_spin_lock > +static __always_inline bool virt_queue_spin_lock(struct qspinlock *lock) > +{ > + return false; > +} > +#endif > + > /* > * Initializier > */ > --- a/kernel/locking/qspinlock.c > +++ b/kernel/locking/qspinlock.c > @@ -247,6 +247,9 @@ void queue_spin_lock_slowpath(struct qsp > > BUILD_BUG_ON(CONFIG_NR_CPUS>= (1U<< _Q_TAIL_CPU_BITS)); > > + if (virt_queue_spin_lock(lock)) > + return; > + > /* > * wait for in-progress pending->locked hand-overs > * I just wonder if it is better to allow the kernel distributors to decide if unfair lock should be the default for virtual guest. Anyway, I have no objection to that myself. -Longman -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Sun, Jun 15, 2014 at 02:47:05PM +0200, Peter Zijlstra wrote: > When we detect a hypervisor (!paravirt, see later patches), revert to Please spell out the name of the patches. > a simple test-and-set lock to avoid the horrors of queue preemption. Heheh. > > Signed-off-by: Peter Zijlstra <peterz@infradead.org> > --- > arch/x86/include/asm/qspinlock.h | 14 ++++++++++++++ > include/asm-generic/qspinlock.h | 7 +++++++ > kernel/locking/qspinlock.c | 3 +++ > 3 files changed, 24 insertions(+) > > --- a/arch/x86/include/asm/qspinlock.h > +++ b/arch/x86/include/asm/qspinlock.h > @@ -1,6 +1,7 @@ > #ifndef _ASM_X86_QSPINLOCK_H > #define _ASM_X86_QSPINLOCK_H > > +#include <asm/cpufeature.h> > #include <asm-generic/qspinlock_types.h> > > #if !defined(CONFIG_X86_OOSTORE) && !defined(CONFIG_X86_PPRO_FENCE) > @@ -20,6 +21,19 @@ static inline void queue_spin_unlock(str > > #endif /* !CONFIG_X86_OOSTORE && !CONFIG_X86_PPRO_FENCE */ > > +#define virt_queue_spin_lock virt_queue_spin_lock > + > +static inline bool virt_queue_spin_lock(struct qspinlock *lock) > +{ > + if (!static_cpu_has(X86_FEATURE_HYPERVISOR)) > + return false; > + > + while (atomic_cmpxchg(&lock->val, 0, _Q_LOCKED_VAL) != 0) > + cpu_relax(); > + > + return true; > +} > + > #include <asm-generic/qspinlock.h> > > #endif /* _ASM_X86_QSPINLOCK_H */ > --- a/include/asm-generic/qspinlock.h > +++ b/include/asm-generic/qspinlock.h > @@ -98,6 +98,13 @@ static __always_inline void queue_spin_u > } > #endif > > +#ifndef virt_queue_spin_lock > +static __always_inline bool virt_queue_spin_lock(struct qspinlock *lock) > +{ > + return false; > +} > +#endif > + > /* > * Initializier > */ > --- a/kernel/locking/qspinlock.c > +++ b/kernel/locking/qspinlock.c > @@ -247,6 +247,9 @@ void queue_spin_lock_slowpath(struct qsp > > BUILD_BUG_ON(CONFIG_NR_CPUS >= (1U << _Q_TAIL_CPU_BITS)); > > + if (virt_queue_spin_lock(lock)) > + return; > + > /* > * wait for in-progress pending->locked hand-overs > * > > -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
--- a/arch/x86/include/asm/qspinlock.h +++ b/arch/x86/include/asm/qspinlock.h @@ -1,6 +1,7 @@ #ifndef _ASM_X86_QSPINLOCK_H #define _ASM_X86_QSPINLOCK_H +#include <asm/cpufeature.h> #include <asm-generic/qspinlock_types.h> #if !defined(CONFIG_X86_OOSTORE) && !defined(CONFIG_X86_PPRO_FENCE) @@ -20,6 +21,19 @@ static inline void queue_spin_unlock(str #endif /* !CONFIG_X86_OOSTORE && !CONFIG_X86_PPRO_FENCE */ +#define virt_queue_spin_lock virt_queue_spin_lock + +static inline bool virt_queue_spin_lock(struct qspinlock *lock) +{ + if (!static_cpu_has(X86_FEATURE_HYPERVISOR)) + return false; + + while (atomic_cmpxchg(&lock->val, 0, _Q_LOCKED_VAL) != 0) + cpu_relax(); + + return true; +} + #include <asm-generic/qspinlock.h> #endif /* _ASM_X86_QSPINLOCK_H */ --- a/include/asm-generic/qspinlock.h +++ b/include/asm-generic/qspinlock.h @@ -98,6 +98,13 @@ static __always_inline void queue_spin_u } #endif +#ifndef virt_queue_spin_lock +static __always_inline bool virt_queue_spin_lock(struct qspinlock *lock) +{ + return false; +} +#endif + /* * Initializier */ --- a/kernel/locking/qspinlock.c +++ b/kernel/locking/qspinlock.c @@ -247,6 +247,9 @@ void queue_spin_lock_slowpath(struct qsp BUILD_BUG_ON(CONFIG_NR_CPUS >= (1U << _Q_TAIL_CPU_BITS)); + if (virt_queue_spin_lock(lock)) + return; + /* * wait for in-progress pending->locked hand-overs *
When we detect a hypervisor (!paravirt, see later patches), revert to a simple test-and-set lock to avoid the horrors of queue preemption. Signed-off-by: Peter Zijlstra <peterz@infradead.org> --- arch/x86/include/asm/qspinlock.h | 14 ++++++++++++++ include/asm-generic/qspinlock.h | 7 +++++++ kernel/locking/qspinlock.c | 3 +++ 3 files changed, 24 insertions(+) -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html