search for: config_nr_cpus

...with Hyper-Threading 16 cores in total. As mentioned in the subject I am using Ubuntu 8.04 64Bit and Xen 3.2 from Ubuntu package. During these tests I hit on some issues, which are not clear to me. I would be thankful for any comments/hints/thoughts on the following topics: 1. I recognized that CONFIG_NR_CPUS is set to 8 in the Ubuntu Xen kernel. However, the Ubuntu server kernel has a limitation of 64. Is there any specific reason for the limitation of 8 in the Xen kernel? 2. After recompiling the kernel with CONFIG_NR_CPUS=16 /proc/cpuinfo still just shows 8 cores, but xm vcpu-list shows the 16 co...

...lock: Pointer to queued spinlock structure @@ -314,12 +318,6 @@ static __always_inline u32 __pv_wait_head_or_lock(struct qspinlock *lock, */ void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val) { - struct mcs_spinlock *prev, *next, *node; - u32 old, tail; - int idx; - - BUILD_BUG_ON(CONFIG_NR_CPUS >= (1U << _Q_TAIL_CPU_BITS)); - if (pv_enabled()) goto pv_queue; @@ -397,6 +395,26 @@ void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val) queue: lockevent_inc(lock_slowpath); pv_queue: + __queued_spin_lock_slowpath_queue(lock); +} +EXPORT_SYMBOL(queued_spin_lock_slow...

...lock: Pointer to queued spinlock structure @@ -314,12 +318,6 @@ static __always_inline u32 __pv_wait_head_or_lock(struct qspinlock *lock, */ void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val) { - struct mcs_spinlock *prev, *next, *node; - u32 old, tail; - int idx; - - BUILD_BUG_ON(CONFIG_NR_CPUS >= (1U << _Q_TAIL_CPU_BITS)); - if (pv_enabled()) goto pv_queue; @@ -397,6 +395,26 @@ void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val) queue: lockevent_inc(lock_slowpath); pv_queue: + __queued_spin_lock_slowpath_queue(lock); +} +EXPORT_SYMBOL(queued_spin_lock_slow...

...OWPATH_FLAG ((__ticket_t)1) > #else > -#define __TICKET_LOCK_INC 1 > #define TICKET_SLOWPATH_FLAG ((__ticket_t)0) > #endif For the !CONFIG_PARAVIRT case, TICKET_LOCK_INC_SHIFT used to be 0, now you are making it one. Probably not an issue, since even people who compile with 128 < CONFIG_NR_CPUS <= 256 will likely have their spinlocks padded out to 32 or 64 bits anyway in most data structures. > -#if (CONFIG_NR_CPUS < (256 / __TICKET_LOCK_INC)) > +#if (CONFIG_NR_CPUS < (256 / __TICKET_LOCK_TAIL_INC)) > typedef u8 __ticket_t; > typedef u16 __ticketpair_t; > #els...

...e TICKET_LOCK_INC_SHIFT 1 +#define __TICKET_LOCK_TAIL_INC (1<<TICKET_LOCK_INC_SHIFT) + #ifdef CONFIG_PARAVIRT_SPINLOCKS -#define __TICKET_LOCK_INC 2 #define TICKET_SLOWPATH_FLAG ((__ticket_t)1) #else -#define __TICKET_LOCK_INC 1 #define TICKET_SLOWPATH_FLAG ((__ticket_t)0) #endif -#if (CONFIG_NR_CPUS < (256 / __TICKET_LOCK_INC)) +#if (CONFIG_NR_CPUS < (256 / __TICKET_LOCK_TAIL_INC)) typedef u8 __ticket_t; typedef u16 __ticketpair_t; #else @@ -19,7 +20,12 @@ typedef u16 __ticket_t; typedef u32 __ticketpair_t; #endif -#define TICKET_LOCK_INC ((__ticket_t)__TICKET_LOCK_INC) +#define...

...e TICKET_LOCK_INC_SHIFT 1 +#define __TICKET_LOCK_TAIL_INC (1<<TICKET_LOCK_INC_SHIFT) + #ifdef CONFIG_PARAVIRT_SPINLOCKS -#define __TICKET_LOCK_INC 2 #define TICKET_SLOWPATH_FLAG ((__ticket_t)1) #else -#define __TICKET_LOCK_INC 1 #define TICKET_SLOWPATH_FLAG ((__ticket_t)0) #endif -#if (CONFIG_NR_CPUS < (256 / __TICKET_LOCK_INC)) +#if (CONFIG_NR_CPUS < (256 / __TICKET_LOCK_TAIL_INC)) typedef u8 __ticket_t; typedef u16 __ticketpair_t; #else @@ -19,7 +20,12 @@ typedef u16 __ticket_t; typedef u32 __ticketpair_t; #endif -#define TICKET_LOCK_INC ((__ticket_t)__TICKET_LOCK_INC) +#define...

...@@ -314,12 +318,6 @@ static __always_inline u32 __pv_wait_head_or_lock(struct qspinlock *lock, > */ > void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val) > { > - struct mcs_spinlock *prev, *next, *node; > - u32 old, tail; > - int idx; > - > - BUILD_BUG_ON(CONFIG_NR_CPUS >= (1U << _Q_TAIL_CPU_BITS)); > - > if (pv_enabled()) > goto pv_queue; > > @@ -397,6 +395,26 @@ void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val) > queue: > lockevent_inc(lock_slowpath); > pv_queue: > + __queued_spin_lock_slowpath_q...

..._INC (1<<TICKET_LOCK_INC_SHIFT) > + > #ifdef CONFIG_PARAVIRT_SPINLOCKS > -#define __TICKET_LOCK_INC 2 > #define TICKET_SLOWPATH_FLAG ((__ticket_t)1) > #else > -#define __TICKET_LOCK_INC 1 > #define TICKET_SLOWPATH_FLAG ((__ticket_t)0) > #endif > > -#if (CONFIG_NR_CPUS< (256 / __TICKET_LOCK_INC)) > +#if (CONFIG_NR_CPUS< (256 / __TICKET_LOCK_TAIL_INC)) > typedef u8 __ticket_t; > typedef u16 __ticketpair_t; > #else > @@ -19,7 +20,12 @@ typedef u16 __ticket_t; > typedef u32 __ticketpair_t; > #endif > > -#define TICKET_LO...

...Still don't like you put it in a separate function, but you don't need the pointer thing. Note how after you fail the trylock_pending() you touch the second (node) cacheline. > @@ -110,6 +184,9 @@ void queue_spin_lock_slowpath(struct qspinlock *lock, u32 val) > > BUILD_BUG_ON(CONFIG_NR_CPUS >= (1U << _Q_TAIL_CPU_BITS)); > > + if (trylock_pending(lock, &val)) > + return; /* Lock acquired */ > + > node = this_cpu_ptr(&mcs_nodes[0]); > idx = node->count++; > tail = encode_tail(smp_processor_id(), idx); > @@ -119,15 +196,18 @@ void queu...

...Still don't like you put it in a separate function, but you don't need the pointer thing. Note how after you fail the trylock_pending() you touch the second (node) cacheline. > @@ -110,6 +184,9 @@ void queue_spin_lock_slowpath(struct qspinlock *lock, u32 val) > > BUILD_BUG_ON(CONFIG_NR_CPUS >= (1U << _Q_TAIL_CPU_BITS)); > > + if (trylock_pending(lock, &val)) > + return; /* Lock acquired */ > + > node = this_cpu_ptr(&mcs_nodes[0]); > idx = node->count++; > tail = encode_tail(smp_processor_id(), idx); > @@ -119,15 +196,18 @@ void queu...

...n of the previous definition In file included from /usr/src/linux/include/linux/prefetch.h:13, from /usr/src/linux/include/linux/list.h:6, from /usr/src/linux/include/linux/module.h:12, from zaptel.c:44: /usr/include/asm/processor.h:75: error: `CONFIG_NR_CPUS' undeclared here (not in a function) In file included from zaptel.c:44: /usr/src/linux/include/linux/module.h:21:34: linux/modversions.h: No such file or directory In file included from /usr/include/asm/smp.h:17, from /usr/src/linux/include/linux/smp.h:14,...

...ways_inline u32 __pv_wait_head_or_lock(struct qspinlock *lock, >> */ >> void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val) >> { >> - struct mcs_spinlock *prev, *next, *node; >> - u32 old, tail; >> - int idx; >> - >> - BUILD_BUG_ON(CONFIG_NR_CPUS >= (1U << _Q_TAIL_CPU_BITS)); >> - >> if (pv_enabled()) >> goto pv_queue; >> >> @@ -397,6 +395,26 @@ void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val) >> queue: >> lockevent_inc(lock_slowpath); >> pv_queue: >...

...ways_inline u32 __pv_wait_head_or_lock(struct qspinlock *lock, >> */ >> void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val) >> { >> - struct mcs_spinlock *prev, *next, *node; >> - u32 old, tail; >> - int idx; >> - >> - BUILD_BUG_ON(CONFIG_NR_CPUS >= (1U << _Q_TAIL_CPU_BITS)); >> - >> if (pv_enabled()) >> goto pv_queue; >> >> @@ -397,6 +395,26 @@ void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val) >> queue: >> lockevent_inc(lock_slowpath); >> pv_queue: >...

...+#endif > barrier(); > ACCESS_ONCE(l->locked) = _Q_LOCKED_VAL; > barrier(); Why? If we have a simple test-and-set lock like below, we'll never get here at all. > @@ -252,6 +260,18 @@ void queue_spin_lock_slowpath(struct qspinlock *lock, u32 val) > > BUILD_BUG_ON(CONFIG_NR_CPUS >= (1U << _Q_TAIL_CPU_BITS)); > > +#ifdef CONFIG_VIRT_UNFAIR_LOCKS > + /* > + * A simple test and set unfair lock > + */ > + if (static_key_false(&virt_unfairlocks_enabled)) { > + cpu_relax(); /* Relax after a failed lock attempt */ Meh, I don't think any...

...+#endif > barrier(); > ACCESS_ONCE(l->locked) = _Q_LOCKED_VAL; > barrier(); Why? If we have a simple test-and-set lock like below, we'll never get here at all. > @@ -252,6 +260,18 @@ void queue_spin_lock_slowpath(struct qspinlock *lock, u32 val) > > BUILD_BUG_ON(CONFIG_NR_CPUS >= (1U << _Q_TAIL_CPU_BITS)); > > +#ifdef CONFIG_VIRT_UNFAIR_LOCKS > + /* > + * A simple test and set unfair lock > + */ > + if (static_key_false(&virt_unfairlocks_enabled)) { > + cpu_relax(); /* Relax after a failed lock attempt */ Meh, I don't think any...

Since Waiman seems incapable of doing simple things; here's my take on the paravirt crap. The first few patches are taken from Waiman's latest series, but the virt support is completely new. Its primary aim is to not mess up the native code. I've not stress tested it, but the virt and paravirt (kvm) cases boot on simple smp guests. I've not done Xen, but the patch should be

Since Waiman seems incapable of doing simple things; here's my take on the paravirt crap. The first few patches are taken from Waiman's latest series, but the virt support is completely new. Its primary aim is to not mess up the native code. I've not stress tested it, but the virt and paravirt (kvm) cases boot on simple smp guests. I've not done Xen, but the patch should be

...ef 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 *

...nged, 10 insertions(+) Index: linux-2.6/kernel/locking/qspinlock.c =================================================================== --- linux-2.6.orig/kernel/locking/qspinlock.c +++ linux-2.6/kernel/locking/qspinlock.c @@ -226,6 +226,16 @@ void queue_spin_lock_slowpath(struct qsp BUILD_BUG_ON(CONFIG_NR_CPUS >= (1U << _Q_TAIL_CPU_BITS)); /* + * wait for in-progress pending->locked hand-overs + * + * 0,1,0 -> 0,0,1 + */ + if (val == _Q_PENDING_VAL) { + while ((val = atomic_read(&lock->val)) == _Q_PENDING_VAL) + cpu_relax(); + } + + /* * trylock || pending * * 0,...

...) +#define TICKET_LOCK_INC_SHIFT 1 +#define __TICKET_LOCK_TAIL_INC (1<<TICKET_LOCK_INC_SHIFT) #else -#define __TICKET_LOCK_INC 1 -#define TICKET_SLOWPATH_FLAG ((__ticket_t)0) +#define TICKET_LOCK_INC_SHIFT 0 +#define __TICKET_LOCK_TAIL_INC (1<<TICKET_LOCK_INC_SHIFT) #endif -#if (CONFIG_NR_CPUS < (256 / __TICKET_LOCK_INC)) +#if (CONFIG_NR_CPUS < (256 / __TICKET_LOCK_TAIL_INC)) typedef u8 __ticket_t; typedef u16 __ticketpair_t; #else @@ -19,7 +20,40 @@ typedef u16 __ticket_t; typedef u32 __ticketpair_t; #endif -#define TICKET_LOCK_INC ((__ticket_t)__TICKET_LOCK_INC) +#ifdef C...