[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-changelog] [xen staging] xen/sched: split schedule_cpu_switch()
commit 2ea514e1b8c9aafb878e926d6199e93c13fedfb9 Author: Juergen Gross <jgross@xxxxxxxx> AuthorDate: Wed Oct 2 09:27:38 2019 +0200 Commit: Jan Beulich <jbeulich@xxxxxxxx> CommitDate: Fri Oct 4 13:00:47 2019 +0200 xen/sched: split schedule_cpu_switch() Instead of letting schedule_cpu_switch() handle moving cpus from and to cpupools, split it into schedule_cpu_add() and schedule_cpu_rm(). This will allow us to drop allocating/freeing scheduler data for free cpus as the idle scheduler doesn't need such data. Signed-off-by: Juergen Gross <jgross@xxxxxxxx> Reviewed-by: Dario Faggioli <dfaggioli@xxxxxxxx> --- xen/common/cpupool.c | 4 +- xen/common/schedule.c | 133 +++++++++++++++++++++++++++--------------------- xen/include/xen/sched.h | 3 +- 3 files changed, 78 insertions(+), 62 deletions(-) diff --git a/xen/common/cpupool.c b/xen/common/cpupool.c index 51f0ff0d88..02825e779d 100644 --- a/xen/common/cpupool.c +++ b/xen/common/cpupool.c @@ -271,7 +271,7 @@ static int cpupool_assign_cpu_locked(struct cpupool *c, unsigned int cpu) if ( (cpupool_moving_cpu == cpu) && (c != cpupool_cpu_moving) ) return -EADDRNOTAVAIL; - ret = schedule_cpu_switch(cpu, c); + ret = schedule_cpu_add(cpu, c); if ( ret ) return ret; @@ -321,7 +321,7 @@ static int cpupool_unassign_cpu_finish(struct cpupool *c) */ if ( !ret ) { - ret = schedule_cpu_switch(cpu, NULL); + ret = schedule_cpu_rm(cpu); if ( ret ) cpumask_clear_cpu(cpu, &cpupool_free_cpus); else diff --git a/xen/common/schedule.c b/xen/common/schedule.c index 067063415d..3a9ae6bf3f 100644 --- a/xen/common/schedule.c +++ b/xen/common/schedule.c @@ -93,15 +93,6 @@ static struct scheduler __read_mostly ops; static void sched_set_affinity( struct sched_unit *unit, const cpumask_t *hard, const cpumask_t *soft); -static spinlock_t * -sched_idle_switch_sched(struct scheduler *new_ops, unsigned int cpu, - void *pdata, void *vdata) -{ - sched_idle_unit(cpu)->priv = NULL; - - return &sched_free_cpu_lock; -} - static struct sched_resource * sched_idle_res_pick(const struct scheduler *ops, const struct sched_unit *unit) { @@ -141,7 +132,6 @@ static struct scheduler sched_idle_ops = { .alloc_udata = sched_idle_alloc_udata, .free_udata = sched_idle_free_udata, - .switch_sched = sched_idle_switch_sched, }; static inline struct vcpu *unit2vcpu_cpu(const struct sched_unit *unit, @@ -2551,36 +2541,22 @@ void __init scheduler_init(void) } /* - * Move a pCPU outside of the influence of the scheduler of its current - * cpupool, or subject it to the scheduler of a new cpupool. - * - * For the pCPUs that are removed from their cpupool, their scheduler becomes - * &sched_idle_ops (the idle scheduler). + * Move a pCPU from free cpus (running the idle scheduler) to a cpupool + * using any "real" scheduler. + * The cpu is still marked as "free" and not yet valid for its cpupool. */ -int schedule_cpu_switch(unsigned int cpu, struct cpupool *c) +int schedule_cpu_add(unsigned int cpu, struct cpupool *c) { struct vcpu *idle; - void *ppriv, *ppriv_old, *vpriv, *vpriv_old; - struct scheduler *old_ops = get_sched_res(cpu)->scheduler; - struct scheduler *new_ops = (c == NULL) ? &sched_idle_ops : c->sched; - struct sched_resource *sd = get_sched_res(cpu); - struct cpupool *old_pool = sd->cpupool; + void *ppriv, *vpriv; + struct scheduler *new_ops = c->sched; + struct sched_resource *sr = get_sched_res(cpu); spinlock_t *old_lock, *new_lock; unsigned long flags; - /* - * pCPUs only move from a valid cpupool to free (i.e., out of any pool), - * or from free to a valid cpupool. In the former case (which happens when - * c is NULL), we want the CPU to have been marked as free already, as - * well as to not be valid for the source pool any longer, when we get to - * here. In the latter case (which happens when c is a valid cpupool), we - * want the CPU to still be marked as free, as well as to not yet be valid - * for the destination pool. - */ - ASSERT(c != old_pool && (c != NULL || old_pool != NULL)); ASSERT(cpumask_test_cpu(cpu, &cpupool_free_cpus)); - ASSERT((c == NULL && !cpumask_test_cpu(cpu, old_pool->cpu_valid)) || - (c != NULL && !cpumask_test_cpu(cpu, c->cpu_valid))); + ASSERT(!cpumask_test_cpu(cpu, c->cpu_valid)); + ASSERT(get_sched_res(cpu)->cpupool == NULL); /* * To setup the cpu for the new scheduler we need: @@ -2605,52 +2581,91 @@ int schedule_cpu_switch(unsigned int cpu, struct cpupool *c) return -ENOMEM; } - sched_do_tick_suspend(old_ops, cpu); - /* - * The actual switch, including (if necessary) the rerouting of the - * scheduler lock to whatever new_ops prefers, needs to happen in one - * critical section, protected by old_ops' lock, or races are possible. - * It is, in fact, the lock of another scheduler that we are taking (the - * scheduler of the cpupool that cpu still belongs to). But that is ok - * as, anyone trying to schedule on this cpu will spin until when we - * release that lock (bottom of this function). When he'll get the lock - * --thanks to the loop inside *_schedule_lock() functions-- he'll notice - * that the lock itself changed, and retry acquiring the new one (which - * will be the correct, remapped one, at that point). + * The actual switch, including the rerouting of the scheduler lock to + * whatever new_ops prefers, needs to happen in one critical section, + * protected by old_ops' lock, or races are possible. + * It is, in fact, the lock of the idle scheduler that we are taking. + * But that is ok as anyone trying to schedule on this cpu will spin until + * when we release that lock (bottom of this function). When he'll get the + * lock --thanks to the loop inside *_schedule_lock() functions-- he'll + * notice that the lock itself changed, and retry acquiring the new one + * (which will be the correct, remapped one, at that point). */ old_lock = pcpu_schedule_lock_irqsave(cpu, &flags); - vpriv_old = idle->sched_unit->priv; - ppriv_old = sd->sched_priv; new_lock = sched_switch_sched(new_ops, cpu, ppriv, vpriv); - sd->scheduler = new_ops; - sd->sched_priv = ppriv; + sr->scheduler = new_ops; + sr->sched_priv = ppriv; /* - * The data above is protected under new_lock, which may be unlocked. - * Another CPU can take new_lock as soon as sd->schedule_lock is visible, - * and must observe all prior initialisation. + * Reroute the lock to the per pCPU lock as /last/ thing. In fact, + * if it is free (and it can be) we want that anyone that manages + * taking it, finds all the initializations we've done above in place. */ smp_wmb(); - sd->schedule_lock = new_lock; + sr->schedule_lock = new_lock; - /* _Not_ pcpu_schedule_unlock(): schedule_lock may have changed! */ + /* _Not_ pcpu_schedule_unlock(): schedule_lock has changed! */ spin_unlock_irqrestore(old_lock, flags); sched_do_tick_resume(new_ops, cpu); + sr->granularity = cpupool_get_granularity(c); + sr->cpupool = c; + /* The cpu is added to a pool, trigger it to go pick up some work */ + cpu_raise_softirq(cpu, SCHEDULE_SOFTIRQ); + + return 0; +} + +/* + * Remove a pCPU from its cpupool. Its scheduler becomes &sched_idle_ops + * (the idle scheduler). + * The cpu is already marked as "free" and not valid any longer for its + * cpupool. + */ +int schedule_cpu_rm(unsigned int cpu) +{ + struct vcpu *idle; + void *ppriv_old, *vpriv_old; + struct sched_resource *sr = get_sched_res(cpu); + struct scheduler *old_ops = sr->scheduler; + spinlock_t *old_lock; + unsigned long flags; + + ASSERT(sr->cpupool != NULL); + ASSERT(cpumask_test_cpu(cpu, &cpupool_free_cpus)); + ASSERT(!cpumask_test_cpu(cpu, sr->cpupool->cpu_valid)); + + idle = idle_vcpu[cpu]; + + sched_do_tick_suspend(old_ops, cpu); + + /* See comment in schedule_cpu_add() regarding lock switching. */ + old_lock = pcpu_schedule_lock_irqsave(cpu, &flags); + + vpriv_old = idle->sched_unit->priv; + ppriv_old = sr->sched_priv; + + idle->sched_unit->priv = NULL; + sr->scheduler = &sched_idle_ops; + sr->sched_priv = NULL; + + smp_mb(); + sr->schedule_lock = &sched_free_cpu_lock; + + /* _Not_ pcpu_schedule_unlock(): schedule_lock may have changed! */ + spin_unlock_irqrestore(old_lock, flags); + sched_deinit_pdata(old_ops, ppriv_old, cpu); sched_free_udata(old_ops, vpriv_old); sched_free_pdata(old_ops, ppriv_old, cpu); - get_sched_res(cpu)->granularity = cpupool_get_granularity(c); - get_sched_res(cpu)->cpupool = c; - /* When a cpu is added to a pool, trigger it to go pick up some work */ - if ( c != NULL ) - cpu_raise_softirq(cpu, SCHEDULE_SOFTIRQ); + sr->granularity = 1; + sr->cpupool = NULL; return 0; } diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h index aa8257edc9..a40bd5fb56 100644 --- a/xen/include/xen/sched.h +++ b/xen/include/xen/sched.h @@ -920,7 +920,8 @@ struct scheduler; struct scheduler *scheduler_get_default(void); struct scheduler *scheduler_alloc(unsigned int sched_id, int *perr); void scheduler_free(struct scheduler *sched); -int schedule_cpu_switch(unsigned int cpu, struct cpupool *c); +int schedule_cpu_add(unsigned int cpu, struct cpupool *c); +int schedule_cpu_rm(unsigned int cpu); void vcpu_set_periodic_timer(struct vcpu *v, s_time_t value); int cpu_disable_scheduler(unsigned int cpu); void sched_setup_dom0_vcpus(struct domain *d); -- generated by git-patchbot for /home/xen/git/xen.git#staging _______________________________________________ Xen-changelog mailing list Xen-changelog@xxxxxxxxxxxxxxxxxxxx https://lists.xenproject.org/xen-changelog
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