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[Xen-devel] [PATCH v2] introduce and use relaxed cpumask bitops

To: "xen-devel" <xen-devel@xxxxxxxxxxxxxxxxxxxx>

From: "Jan Beulich" <JBeulich@xxxxxxxx>

Date: Wed, 11 Feb 2015 13:42:26 +0000

Cc: Keir Fraser <keir@xxxxxxx>, George Dunlap <George.Dunlap@xxxxxxxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>, Tim Deegan <tim@xxxxxxx>, Ian Campbell <Ian.Campbell@xxxxxxxxxxxxx>

Delivery-date: Wed, 11 Feb 2015 13:42:40 +0000

List-id: Xen developer discussion <xen-devel.lists.xen.org>

Using atomic (LOCKed on x86) bitops for certain of the operations on cpumask_t is overkill when the variables aren't concurrently accessible (e.g. local function variables, or due to explicit locking). Introduce alternatives using non-atomic bitops and use them where appropriate. Note that this - adds a volatile qualifier to cpumask_test_and_{clear,set}_cpu() (should have been there from the beginning, like is the case for cpumask_{clear,set}_cpu()) - replaces several cpumask_clear()+cpumask_set_cpu(, n) pairs by the simpler cpumask_copy(, cpumask_of(n)) (or just cpumask_of(n) if we can do without copying) Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx> Acked-by: George Dunlap <george.dunlap@xxxxxxxxxxxxx> --- v2: Make naming of new functions consistent with exisiting ones. --- a/xen/arch/x86/hpet.c +++ b/xen/arch/x86/hpet.c @@ -158,7 +158,7 @@ static void evt_do_broadcast(cpumask_t * { unsigned int cpu = smp_processor_id(); - if ( cpumask_test_and_clear_cpu(cpu, mask) ) + if ( __cpumask_test_and_clear_cpu(cpu, mask) ) raise_softirq(TIMER_SOFTIRQ); cpuidle_wakeup_mwait(mask); @@ -197,7 +197,7 @@ again: continue; if ( deadline <= now ) - cpumask_set_cpu(cpu, &mask); + __cpumask_set_cpu(cpu, &mask); else if ( deadline < next_event ) next_event = deadline; } --- a/xen/arch/x86/irq.c +++ b/xen/arch/x86/irq.c @@ -1450,7 +1450,7 @@ void desc_guest_eoi(struct irq_desc *des cpumask_copy(&cpu_eoi_map, action->cpu_eoi_map); - if ( cpumask_test_and_clear_cpu(smp_processor_id(), &cpu_eoi_map) ) + if ( __cpumask_test_and_clear_cpu(smp_processor_id(), &cpu_eoi_map) ) { __set_eoi_ready(desc); spin_unlock(&desc->lock); --- a/xen/arch/x86/mm.c +++ b/xen/arch/x86/mm.c @@ -3216,7 +3216,7 @@ long do_mmuext_op( for_each_online_cpu(cpu) if ( !cpumask_intersects(&mask, per_cpu(cpu_sibling_mask, cpu)) ) - cpumask_set_cpu(cpu, &mask); + __cpumask_set_cpu(cpu, &mask); flush_mask(&mask, FLUSH_CACHE); } else --- a/xen/arch/x86/platform_hypercall.c +++ b/xen/arch/x86/platform_hypercall.c @@ -489,7 +489,7 @@ ret_t do_platform_op(XEN_GUEST_HANDLE_PA if ( !idletime ) { - cpumask_clear_cpu(cpu, cpumap); + __cpumask_clear_cpu(cpu, cpumap); continue; } --- a/xen/arch/x86/time.c +++ b/xen/arch/x86/time.c @@ -179,7 +179,7 @@ static void smp_send_timer_broadcast_ipi if ( cpumask_test_cpu(cpu, &mask) ) { - cpumask_clear_cpu(cpu, &mask); + __cpumask_clear_cpu(cpu, &mask); raise_softirq(TIMER_SOFTIRQ); } --- a/xen/common/core_parking.c +++ b/xen/common/core_parking.c @@ -75,11 +75,10 @@ static unsigned int core_parking_perform if ( core_weight < core_tmp ) { core_weight = core_tmp; - cpumask_clear(&core_candidate_map); - cpumask_set_cpu(cpu, &core_candidate_map); + cpumask_copy(&core_candidate_map, cpumask_of(cpu)); } else if ( core_weight == core_tmp ) - cpumask_set_cpu(cpu, &core_candidate_map); + __cpumask_set_cpu(cpu, &core_candidate_map); } for_each_cpu(cpu, &core_candidate_map) @@ -88,11 +87,10 @@ static unsigned int core_parking_perform if ( sibling_weight < sibling_tmp ) { sibling_weight = sibling_tmp; - cpumask_clear(&sibling_candidate_map); - cpumask_set_cpu(cpu, &sibling_candidate_map); + cpumask_copy(&sibling_candidate_map, cpumask_of(cpu)); } else if ( sibling_weight == sibling_tmp ) - cpumask_set_cpu(cpu, &sibling_candidate_map); + __cpumask_set_cpu(cpu, &sibling_candidate_map); } cpu = cpumask_first(&sibling_candidate_map); @@ -135,11 +133,10 @@ static unsigned int core_parking_power(u if ( core_weight > core_tmp ) { core_weight = core_tmp; - cpumask_clear(&core_candidate_map); - cpumask_set_cpu(cpu, &core_candidate_map); + cpumask_copy(&core_candidate_map, cpumask_of(cpu)); } else if ( core_weight == core_tmp ) - cpumask_set_cpu(cpu, &core_candidate_map); + __cpumask_set_cpu(cpu, &core_candidate_map); } for_each_cpu(cpu, &core_candidate_map) @@ -148,11 +145,10 @@ static unsigned int core_parking_power(u if ( sibling_weight > sibling_tmp ) { sibling_weight = sibling_tmp; - cpumask_clear(&sibling_candidate_map); - cpumask_set_cpu(cpu, &sibling_candidate_map); + cpumask_copy(&sibling_candidate_map, cpumask_of(cpu)); } else if ( sibling_weight == sibling_tmp ) - cpumask_set_cpu(cpu, &sibling_candidate_map); + __cpumask_set_cpu(cpu, &sibling_candidate_map); } cpu = cpumask_first(&sibling_candidate_map); --- a/xen/common/cpu.c +++ b/xen/common/cpu.c @@ -192,7 +192,7 @@ int disable_nonboot_cpus(void) break; } - cpumask_set_cpu(cpu, &frozen_cpus); + __cpumask_set_cpu(cpu, &frozen_cpus); } BUG_ON(!error && (num_online_cpus() != 1)); --- a/xen/common/page_alloc.c +++ b/xen/common/page_alloc.c @@ -1337,7 +1337,7 @@ static int __init find_non_smt(unsigned if ( cpumask_intersects(dest, per_cpu(cpu_sibling_mask, i)) ) continue; cpu = cpumask_first(per_cpu(cpu_sibling_mask, i)); - cpumask_set_cpu(cpu, dest); + __cpumask_set_cpu(cpu, dest); } return cpumask_weight(dest); } @@ -1449,7 +1449,7 @@ void __init scrub_heap_pages(void) cpus = find_non_smt(best_node, &node_cpus); if ( cpus == 0 ) { - cpumask_set_cpu(smp_processor_id(), &node_cpus); + __cpumask_set_cpu(smp_processor_id(), &node_cpus); cpus = 1; } /* We already have the node information from round #0. */ --- a/xen/common/sched_credit.c +++ b/xen/common/sched_credit.c @@ -372,7 +372,7 @@ __runq_tickle(unsigned int cpu, struct c { if ( cur->pri != CSCHED_PRI_IDLE ) SCHED_STAT_CRANK(tickle_idlers_none); - cpumask_set_cpu(cpu, &mask); + __cpumask_set_cpu(cpu, &mask); } else if ( !idlers_empty ) { @@ -422,7 +422,7 @@ __runq_tickle(unsigned int cpu, struct c SCHED_VCPU_STAT_CRANK(cur, migrate_r); SCHED_STAT_CRANK(migrate_kicked_away); set_bit(_VPF_migrating, &cur->vcpu->pause_flags); - cpumask_set_cpu(cpu, &mask); + __cpumask_set_cpu(cpu, &mask); } else if ( !new_idlers_empty ) { @@ -432,7 +432,7 @@ __runq_tickle(unsigned int cpu, struct c { this_cpu(last_tickle_cpu) = cpumask_cycle(this_cpu(last_tickle_cpu), &idle_mask); - cpumask_set_cpu(this_cpu(last_tickle_cpu), &mask); + __cpumask_set_cpu(this_cpu(last_tickle_cpu), &mask); } else cpumask_or(&mask, &mask, &idle_mask); @@ -675,7 +675,7 @@ _csched_cpu_pick(const struct scheduler */ cpumask_and(&idlers, &cpu_online_map, CSCHED_PRIV(ops)->idlers); if ( vc->processor == cpu && IS_RUNQ_IDLE(cpu) ) - cpumask_set_cpu(cpu, &idlers); + __cpumask_set_cpu(cpu, &idlers); cpumask_and(&cpus, &cpus, &idlers); /* @@ -692,7 +692,7 @@ _csched_cpu_pick(const struct scheduler */ if ( !cpumask_test_cpu(cpu, &cpus) && !cpumask_empty(&cpus) ) cpu = cpumask_cycle(cpu, &cpus); - cpumask_clear_cpu(cpu, &cpus); + __cpumask_clear_cpu(cpu, &cpus); while ( !cpumask_empty(&cpus) ) { @@ -1536,7 +1536,7 @@ csched_load_balance(struct csched_privat /* Find out what the !idle are in this node */ cpumask_andnot(&workers, online, prv->idlers); cpumask_and(&workers, &workers, &node_to_cpumask(peer_node)); - cpumask_clear_cpu(cpu, &workers); + __cpumask_clear_cpu(cpu, &workers); peer_cpu = cpumask_first(&workers); if ( peer_cpu >= nr_cpu_ids ) --- a/xen/common/sched_rt.c +++ b/xen/common/sched_rt.c @@ -663,7 +663,7 @@ burn_budget(const struct scheduler *ops, * lock is grabbed before calling this function */ static struct rt_vcpu * -__runq_pick(const struct scheduler *ops, cpumask_t *mask) +__runq_pick(const struct scheduler *ops, const cpumask_t *mask) { struct list_head *runq = rt_runq(ops); struct list_head *iter; @@ -780,10 +780,7 @@ rt_schedule(const struct scheduler *ops, } else { - cpumask_t cur_cpu; - cpumask_clear(&cur_cpu); - cpumask_set_cpu(cpu, &cur_cpu); - snext = __runq_pick(ops, &cur_cpu); + snext = __runq_pick(ops, cpumask_of(cpu)); if ( snext == NULL ) snext = rt_vcpu(idle_vcpu[cpu]); --- a/xen/common/softirq.c +++ b/xen/common/softirq.c @@ -88,7 +88,7 @@ void cpumask_raise_softirq(const cpumask if ( !test_and_set_bit(nr, &softirq_pending(cpu)) && cpu != this_cpu && !arch_skip_send_event_check(cpu) ) - cpumask_set_cpu(cpu, raise_mask); + __cpumask_set_cpu(cpu, raise_mask); if ( raise_mask == &send_mask ) smp_send_event_check_mask(raise_mask); @@ -106,7 +106,7 @@ void cpu_raise_softirq(unsigned int cpu, if ( !per_cpu(batching, this_cpu) || in_irq() ) smp_send_event_check_cpu(cpu); else - set_bit(nr, &per_cpu(batch_mask, this_cpu)); + __cpumask_set_cpu(nr, &per_cpu(batch_mask, this_cpu)); } void cpu_raise_softirq_batch_begin(void) @@ -122,7 +122,7 @@ void cpu_raise_softirq_batch_finish(void ASSERT(per_cpu(batching, this_cpu)); for_each_cpu ( cpu, mask ) if ( !softirq_pending(cpu) ) - cpumask_clear_cpu(cpu, mask); + __cpumask_clear_cpu(cpu, mask); smp_send_event_check_mask(mask); cpumask_clear(mask); --per_cpu(batching, this_cpu); --- a/xen/include/xen/cpumask.h +++ b/xen/include/xen/cpumask.h @@ -103,11 +103,21 @@ static inline void cpumask_set_cpu(int c set_bit(cpumask_check(cpu), dstp->bits); } +static inline void __cpumask_set_cpu(int cpu, cpumask_t *dstp) +{ + __set_bit(cpumask_check(cpu), dstp->bits); +} + static inline void cpumask_clear_cpu(int cpu, volatile cpumask_t *dstp) { clear_bit(cpumask_check(cpu), dstp->bits); } +static inline void __cpumask_clear_cpu(int cpu, cpumask_t *dstp) +{ + __clear_bit(cpumask_check(cpu), dstp->bits); +} + static inline void cpumask_setall(cpumask_t *dstp) { bitmap_fill(dstp->bits, nr_cpumask_bits); @@ -122,16 +132,26 @@ static inline void cpumask_clear(cpumask #define cpumask_test_cpu(cpu, cpumask) \ test_bit(cpumask_check(cpu), (cpumask)->bits) -static inline int cpumask_test_and_set_cpu(int cpu, cpumask_t *addr) +static inline int cpumask_test_and_set_cpu(int cpu, volatile cpumask_t *addr) { return test_and_set_bit(cpumask_check(cpu), addr->bits); } -static inline int cpumask_test_and_clear_cpu(int cpu, cpumask_t *addr) +static inline int __cpumask_test_and_set_cpu(int cpu, cpumask_t *addr) +{ + return __test_and_set_bit(cpumask_check(cpu), addr->bits); +} + +static inline int cpumask_test_and_clear_cpu(int cpu, volatile cpumask_t *addr) { return test_and_clear_bit(cpumask_check(cpu), addr->bits); } +static inline int __cpumask_test_and_clear_cpu(int cpu, cpumask_t *addr) +{ + return __test_and_clear_bit(cpumask_check(cpu), addr->bits); +} + static inline void cpumask_and(cpumask_t *dstp, const cpumask_t *src1p, const cpumask_t *src2p) {

Attachment: cpumask-relax.patch
Description: Text document

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