xref: /xen/xen/common/sched/private.h

/******************************************************************************
 * Additional declarations for the generic scheduler interface.  This should
 * only be included by files that implement conforming schedulers.
 *
 * Portions by Mark Williamson are (C) 2004 Intel Research Cambridge
 */

#ifndef __XEN_SCHED_IF_H__
#define __XEN_SCHED_IF_H__

#include <xen/err.h>
#include <xen/list.h>
#include <xen/percpu.h>
#include <xen/rcupdate.h>

/* cpus currently in no cpupool */
extern cpumask_t cpupool_free_cpus;

/* Scheduler generic parameters
 * */
#define SCHED_DEFAULT_RATELIMIT_US 1000
extern int sched_ratelimit_us;

/* Scheduling resource mask. */
extern cpumask_t sched_res_mask;

/* Number of vcpus per struct sched_unit. */
enum sched_gran {
    SCHED_GRAN_cpu,
    SCHED_GRAN_core,
    SCHED_GRAN_socket
};

/*
 * In order to allow a scheduler to remap the lock->cpu mapping,
 * we have a per-cpu pointer, along with a pre-allocated set of
 * locks.  The generic schedule init code will point each schedule lock
 * pointer to the schedule lock; if the scheduler wants to remap them,
 * it can simply modify the schedule locks.
 *
 * For cache betterness, keep the actual lock in the same cache area
 * as the rest of the struct.  Just have the scheduler point to the
 * one it wants (This may be the one right in front of it).
 */
struct sched_resource {
    struct scheduler   *scheduler;
    struct cpupool     *cpupool;
    spinlock_t         *schedule_lock,
                       _lock;
    struct sched_unit  *curr;
    struct sched_unit  *sched_unit_idle;
    struct sched_unit  *prev;
    void               *sched_priv;
    struct timer        s_timer;        /* scheduling timer                */

    /* Cpu with lowest id in scheduling resource. */
    unsigned int        master_cpu;
    unsigned int        granularity;
    cpumask_var_t       cpus;           /* cpus covered by this struct     */
    struct rcu_head     rcu;
};

DECLARE_PER_CPU(struct sched_resource *, sched_res);
extern rcu_read_lock_t sched_res_rculock;

static inline struct sched_resource *get_sched_res(unsigned int cpu)
{
    return rcu_dereference(per_cpu(sched_res, cpu));
}

static inline void set_sched_res(unsigned int cpu, struct sched_resource *res)
{
    rcu_assign_pointer(per_cpu(sched_res, cpu), res);
}

static inline struct sched_unit *curr_on_cpu(unsigned int cpu)
{
    return get_sched_res(cpu)->curr;
}

static inline bool is_idle_unit(const struct sched_unit *unit)
{
    return is_idle_vcpu(unit->vcpu_list);
}

/* Returns true if at least one vcpu of the unit is online. */
static inline bool is_unit_online(const struct sched_unit *unit)
{
    const struct vcpu *v;

    for_each_sched_unit_vcpu ( unit, v )
        if ( is_vcpu_online(v) )
            return true;

    return false;
}

static inline unsigned int unit_running(const struct sched_unit *unit)
{
    return unit->runstate_cnt[RUNSTATE_running];
}

/* Returns true if at least one vcpu of the unit is runnable. */
static inline bool unit_runnable(const struct sched_unit *unit)
{
    const struct vcpu *v;

    for_each_sched_unit_vcpu ( unit, v )
        if ( vcpu_runnable(v) )
            return true;

    return false;
}

static inline int vcpu_runstate_blocked(const struct vcpu *v)
{
    return (v->pause_flags & VPF_blocked) ? RUNSTATE_blocked : RUNSTATE_offline;
}

/*
 * Returns whether a sched_unit is runnable and sets new_state for each of its
 * vcpus. It is mandatory to determine the new runstate for all vcpus of a unit
 * without dropping the schedule lock (which happens when synchronizing the
 * context switch of the vcpus of a unit) in order to avoid races with e.g.
 * vcpu_sleep().
 */
static inline bool unit_runnable_state(const struct sched_unit *unit)
{
    struct vcpu *v;
    bool runnable, ret = false;

    if ( is_idle_unit(unit) )
        return true;

    for_each_sched_unit_vcpu ( unit, v )
    {
        runnable = vcpu_runnable(v);

        v->new_state = runnable ? RUNSTATE_running : vcpu_runstate_blocked(v);

        if ( runnable )
            ret = true;
    }

    return ret;
}

static inline void sched_set_res(struct sched_unit *unit,
                                 struct sched_resource *res)
{
    unsigned int cpu = cpumask_first(res->cpus);
    struct vcpu *v;

    for_each_sched_unit_vcpu ( unit, v )
    {
        ASSERT(cpu < nr_cpu_ids);
        v->processor = cpu;
        cpu = cpumask_next(cpu, res->cpus);
    }

    unit->res = res;
}

/* Return master cpu of the scheduling resource the unit is assigned to. */
static inline unsigned int sched_unit_master(const struct sched_unit *unit)
{
    return unit->res->master_cpu;
}

/* Set a bit in pause_flags of all vcpus of a unit. */
static inline void sched_set_pause_flags(struct sched_unit *unit,
                                         unsigned int bit)
{
    struct vcpu *v;

    for_each_sched_unit_vcpu ( unit, v )
        set_bit(bit, &v->pause_flags);
}

/* Clear a bit in pause_flags of all vcpus of a unit. */
static inline void sched_clear_pause_flags(struct sched_unit *unit,
                                           unsigned int bit)
{
    struct vcpu *v;

    for_each_sched_unit_vcpu ( unit, v )
        clear_bit(bit, &v->pause_flags);
}

static inline struct sched_unit *sched_idle_unit(unsigned int cpu)
{
    return get_sched_res(cpu)->sched_unit_idle;
}

static inline unsigned int sched_get_resource_cpu(unsigned int cpu)
{
    return get_sched_res(cpu)->master_cpu;
}

/*
 * Scratch space, for avoiding having too many cpumask_t on the stack.
 * Within each scheduler, when using the scratch mask of one pCPU:
 * - the pCPU must belong to the scheduler,
 * - the caller must own the per-pCPU scheduler lock (a.k.a. runqueue
 *   lock).
 */
DECLARE_PER_CPU(cpumask_t, cpumask_scratch);
#define cpumask_scratch        (&this_cpu(cpumask_scratch))
#define cpumask_scratch_cpu(c) (&per_cpu(cpumask_scratch, c))

/*
 * Deal with _spin_lock_irqsave() returning the flags value instead of storing
 * it in a passed parameter.
 */
#define _sched_spinlock0(lock, irq) _spin_lock##irq(lock)
#define _sched_spinlock1(lock, irq, arg) ({ \
    BUILD_BUG_ON(sizeof(arg) != sizeof(unsigned long)); \
    (arg) = _spin_lock##irq(lock); \
})

#define _sched_spinlock__(nr) _sched_spinlock ## nr
#define _sched_spinlock_(nr)  _sched_spinlock__(nr)
#define _sched_spinlock(lock, irq, args...) \
    _sched_spinlock_(count_args(args))(lock, irq, ## args)

#define sched_lock(kind, param, cpu, irq, arg...) \
static always_inline spinlock_t \
*kind##_schedule_lock##irq(param EXTRA_TYPE(arg)) \
{ \
    for ( ; ; ) \
    { \
        spinlock_t *lock = get_sched_res(cpu)->schedule_lock; \
        /* \
         * v->processor may change when grabbing the lock; but \
         * per_cpu(v->processor) may also change, if changing cpu pool \
         * also changes the scheduler lock.  Retry until they match. \
         * \
         * It may also be the case that v->processor may change but the \
         * lock may be the same; this will succeed in that case. \
         * \
         * Use the speculation unsafe locking helper, there's a speculation \
         * barrier before returning to the caller. \
         */ \
        _sched_spinlock(lock, irq, ## arg); \
        if ( likely(lock == get_sched_res(cpu)->schedule_lock) ) \
        { \
            block_lock_speculation(); \
            return lock; \
        } \
        spin_unlock##irq(lock, ## arg); \
    } \
}

#define sched_unlock(kind, param, cpu, irq, arg...) \
static inline void kind##_schedule_unlock##irq(spinlock_t *lock \
                                               EXTRA_TYPE(arg), param) \
{ \
    ASSERT(lock == get_sched_res(cpu)->schedule_lock); \
    spin_unlock##irq(lock, ## arg); \
}

#define EXTRA_TYPE(arg)
sched_lock(pcpu, unsigned int cpu,     cpu, )
sched_lock(unit, const struct sched_unit *i, i->res->master_cpu, )
sched_lock(pcpu, unsigned int cpu,     cpu,          _irq)
sched_lock(unit, const struct sched_unit *i, i->res->master_cpu, _irq)
sched_unlock(pcpu, unsigned int cpu,     cpu, )
sched_unlock(unit, const struct sched_unit *i, i->res->master_cpu, )
sched_unlock(pcpu, unsigned int cpu,     cpu,          _irq)
sched_unlock(unit, const struct sched_unit *i, i->res->master_cpu, _irq)
#undef EXTRA_TYPE

#define EXTRA_TYPE(arg) , unsigned long arg
#define spin_unlock_irqsave spin_unlock_irqrestore
sched_lock(pcpu, unsigned int cpu,     cpu,          _irqsave, *flags)
sched_lock(unit, const struct sched_unit *i, i->res->master_cpu, _irqsave, *flags)
#undef spin_unlock_irqsave
sched_unlock(pcpu, unsigned int cpu,     cpu,          _irqrestore, flags)
sched_unlock(unit, const struct sched_unit *i, i->res->master_cpu, _irqrestore, flags)
#undef EXTRA_TYPE

#undef sched_unlock
#undef sched_lock

static inline spinlock_t *pcpu_schedule_trylock(unsigned int cpu)
{
    spinlock_t *lock = get_sched_res(cpu)->schedule_lock;

    if ( !spin_trylock(lock) )
        return NULL;
    if ( lock == get_sched_res(cpu)->schedule_lock )
        return lock;
    spin_unlock(lock);
    return NULL;
}

struct scheduler {
    const char *name;       /* full name for this scheduler      */
    const char *opt_name;   /* option name for this scheduler    */
    unsigned int sched_id;  /* ID for this scheduler             */
    void *sched_data;       /* global data pointer               */
    struct cpupool *cpupool;/* points to this scheduler's pool   */

    int          (*global_init)    (void);

    int          (*init)           (struct scheduler *ops);
    void         (*deinit)         (struct scheduler *ops);

    void         (*free_udata)     (const struct scheduler *ops, void *priv);
    void *       (*alloc_udata)    (const struct scheduler *ops,
                                    struct sched_unit *unit, void *dd);

    void         (*free_pdata)     (const struct scheduler *ops,
                                    void *pcpu, int cpu);
    void *       (*alloc_pdata)    (const struct scheduler *ops, int cpu);
    void         (*deinit_pdata)   (const struct scheduler *ops,
                                    void *pcpu, int cpu);

    /* Returns ERR_PTR(-err) for error, NULL for 'nothing needed'. */
    void *       (*alloc_domdata)  (const struct scheduler *ops,
                                    struct domain *dom);
    /* Idempotent. */
    void         (*free_domdata)   (const struct scheduler *ops, void *data);

    spinlock_t * (*switch_sched)   (struct scheduler *new_ops, unsigned int cpu,
                                    void *pdata, void *vdata);

    /* Activate / deactivate units in a cpu pool */
    void         (*insert_unit)    (const struct scheduler *ops,
                                    struct sched_unit *unit);
    void         (*remove_unit)    (const struct scheduler *ops,
                                    struct sched_unit *unit);

    void         (*sleep)          (const struct scheduler *ops,
                                    struct sched_unit *unit);
    void         (*wake)           (const struct scheduler *ops,
                                    struct sched_unit *unit);
    void         (*yield)          (const struct scheduler *ops,
                                    struct sched_unit *unit);
    void         (*context_saved)  (const struct scheduler *ops,
                                    struct sched_unit *unit);

    void         (*do_schedule)    (const struct scheduler *ops,
                                    struct sched_unit *currunit, s_time_t now,
                                    bool tasklet_work_scheduled);

    struct sched_resource *(*pick_resource)(const struct scheduler *ops,
                                            const struct sched_unit *unit);
    void         (*migrate)        (const struct scheduler *ops,
                                    struct sched_unit *unit,
                                    unsigned int new_cpu);
    int          (*adjust)         (const struct scheduler *ops,
                                    struct domain *d,
                                    struct xen_domctl_scheduler_op *op);
    void         (*adjust_affinity)(const struct scheduler *ops,
                                    struct sched_unit *unit,
                                    const struct cpumask *hard,
                                    const struct cpumask *soft);
    int          (*adjust_global)  (const struct scheduler *ops,
                                    struct xen_sysctl_scheduler_op *sc);
    void         (*dump_settings)  (const struct scheduler *ops);
    void         (*dump_cpu_state) (const struct scheduler *ops, int cpu);
    void         (*move_timers)    (const struct scheduler *ops,
                                    struct sched_resource *sr);
};

static inline int sched_init(struct scheduler *s)
{
    return s->init(s);
}

static inline void sched_deinit(struct scheduler *s)
{
    s->deinit(s);
}

static inline spinlock_t *sched_switch_sched(struct scheduler *s,
                                             unsigned int cpu,
                                             void *pdata, void *vdata)
{
    return s->switch_sched(s, cpu, pdata, vdata);
}

static inline void sched_dump_settings(const struct scheduler *s)
{
    if ( s->dump_settings )
        s->dump_settings(s);
}

static inline void sched_dump_cpu_state(const struct scheduler *s, int cpu)
{
    if ( s->dump_cpu_state )
        s->dump_cpu_state(s, cpu);
}

static inline void *sched_alloc_domdata(const struct scheduler *s,
                                        struct domain *d)
{
    return s->alloc_domdata ? s->alloc_domdata(s, d) : NULL;
}

static inline void sched_free_domdata(const struct scheduler *s,
                                      void *data)
{
    ASSERT(s->free_domdata || !data);
    if ( s->free_domdata )
        s->free_domdata(s, data);
}

static inline void *sched_alloc_pdata(const struct scheduler *s, int cpu)
{
    return s->alloc_pdata ? s->alloc_pdata(s, cpu) : NULL;
}

static inline void sched_free_pdata(const struct scheduler *s, void *data,
                                    int cpu)
{
    ASSERT(s->free_pdata || !data);
    if ( s->free_pdata )
        s->free_pdata(s, data, cpu);
}

static inline void sched_deinit_pdata(const struct scheduler *s, void *data,
                                      int cpu)
{
    if ( s->deinit_pdata )
        s->deinit_pdata(s, data, cpu);
}

static inline void *sched_alloc_udata(const struct scheduler *s,
                                      struct sched_unit *unit, void *dom_data)
{
    return s->alloc_udata(s, unit, dom_data);
}

static inline void sched_free_udata(const struct scheduler *s, void *data)
{
    s->free_udata(s, data);
}

static inline void sched_insert_unit(const struct scheduler *s,
                                     struct sched_unit *unit)
{
    if ( s->insert_unit )
        s->insert_unit(s, unit);
}

static inline void sched_remove_unit(const struct scheduler *s,
                                     struct sched_unit *unit)
{
    if ( s->remove_unit )
        s->remove_unit(s, unit);
}

static inline void sched_sleep(const struct scheduler *s,
                               struct sched_unit *unit)
{
    if ( s->sleep )
        s->sleep(s, unit);
}

static inline void sched_wake(const struct scheduler *s,
                              struct sched_unit *unit)
{
    if ( s->wake )
        s->wake(s, unit);
}

static inline void sched_yield(const struct scheduler *s,
                               struct sched_unit *unit)
{
    if ( s->yield )
        s->yield(s, unit);
}

static inline void sched_context_saved(const struct scheduler *s,
                                       struct sched_unit *unit)
{
    if ( s->context_saved )
        s->context_saved(s, unit);
}

static inline void sched_migrate(const struct scheduler *s,
                                 struct sched_unit *unit, unsigned int cpu)
{
    if ( s->migrate )
        s->migrate(s, unit, cpu);
    else
        sched_set_res(unit, get_sched_res(cpu));
}

static inline struct sched_resource *sched_pick_resource(
    const struct scheduler *s, const struct sched_unit *unit)
{
    return s->pick_resource(s, unit);
}

static inline void sched_adjust_affinity(const struct scheduler *s,
                                         struct sched_unit *unit,
                                         const cpumask_t *hard,
                                         const cpumask_t *soft)
{
    if ( s->adjust_affinity )
        s->adjust_affinity(s, unit, hard, soft);
}

static inline int sched_adjust_dom(const struct scheduler *s, struct domain *d,
                                   struct xen_domctl_scheduler_op *op)
{
    return s->adjust ? s->adjust(s, d, op) : 0;
}

static inline int sched_adjust_cpupool(const struct scheduler *s,
                                       struct xen_sysctl_scheduler_op *op)
{
    return s->adjust_global ? s->adjust_global(s, op) : 0;
}

static inline void sched_move_timers(const struct scheduler *s,
                                     struct sched_resource *sr)
{
    if ( s->move_timers )
        s->move_timers(s, sr);
}

static inline void sched_unit_pause_nosync(const struct sched_unit *unit)
{
    struct vcpu *v;

    for_each_sched_unit_vcpu ( unit, v )
        vcpu_pause_nosync(v);
}

static inline void sched_unit_unpause(const struct sched_unit *unit)
{
    struct vcpu *v;

    for_each_sched_unit_vcpu ( unit, v )
        vcpu_unpause(v);
}

#define REGISTER_SCHEDULER(x) static const struct scheduler *x##_entry \
  __used_section(".data.schedulers") = &(x)

struct cpupool
{
    unsigned int     cpupool_id;
#define CPUPOOLID_NONE    (~0U)
    unsigned int     n_dom;
    cpumask_var_t    cpu_valid;      /* all cpus assigned to pool */
    cpumask_var_t    res_valid;      /* all scheduling resources of pool */
    struct list_head list;
    struct cpupool   *next;
    struct scheduler *sched;
    atomic_t         refcnt;
    enum sched_gran  gran;
    unsigned int     sched_gran;     /* Number of cpus per sched-item. */
};

static inline cpumask_t *cpupool_domain_master_cpumask(const struct domain *d)
{
    /*
     * d->cpupool is NULL only for the idle domain, and no one should
     * be interested in calling this for the idle domain.
     */
    ASSERT(d->cpupool != NULL);
    return d->cpupool->res_valid;
}

unsigned int cpupool_get_granularity(const struct cpupool *c);

/*
 * Hard and soft affinity load balancing.
 *
 * Idea is each vcpu has some pcpus that it prefers, some that it does not
 * prefer but is OK with, and some that it cannot run on at all. The first
 * set of pcpus are the ones that are both in the soft affinity *and* in the
 * hard affinity; the second set of pcpus are the ones that are in the hard
 * affinity but *not* in the soft affinity; the third set of pcpus are the
 * ones that are not in the hard affinity.
 *
 * We implement a two step balancing logic. Basically, every time there is
 * the need to decide where to run a vcpu, we first check the soft affinity
 * (well, actually, the && between soft and hard affinity), to see if we can
 * send it where it prefers to (and can) run on. However, if the first step
 * does not find any suitable and free pcpu, we fall back checking the hard
 * affinity.
 */
#define BALANCE_SOFT_AFFINITY    0
#define BALANCE_HARD_AFFINITY    1

#define for_each_affinity_balance_step(step) \
    for ( (step) = 0; (step) <= BALANCE_HARD_AFFINITY; (step)++ )

/*
 * Hard affinity balancing is always necessary and must never be skipped.
 * But soft affinity need only be considered when it has a functionally
 * different effect than other constraints (such as hard affinity, cpus
 * online, or cpupools).
 *
 * Soft affinity only needs to be considered if:
 * * The cpus in the cpupool are not a subset of soft affinity
 * * The hard affinity is not a subset of soft affinity
 * * There is an overlap between the soft and hard affinity masks
 */
static inline bool has_soft_affinity(const struct sched_unit *unit)
{
    return unit->soft_aff_effective &&
           !cpumask_subset(cpupool_domain_master_cpumask(unit->domain),
                           unit->cpu_soft_affinity);
}

/*
 * This function copies in mask the cpumask that should be used for a
 * particular affinity balancing step. For the soft affinity one, the pcpus
 * that are not part of vc's hard affinity are filtered out from the result,
 * to avoid running a vcpu where it would like, but is not allowed to!
 */
static inline void
affinity_balance_cpumask(const struct sched_unit *unit, int step,
                         cpumask_t *mask)
{
    if ( step == BALANCE_SOFT_AFFINITY )
    {
        cpumask_and(mask, unit->cpu_soft_affinity, unit->cpu_hard_affinity);

        if ( unlikely(cpumask_empty(mask)) )
            cpumask_copy(mask, unit->cpu_hard_affinity);
    }
    else /* step == BALANCE_HARD_AFFINITY */
        cpumask_copy(mask, unit->cpu_hard_affinity);
}

struct affinity_masks {
    cpumask_var_t hard;
    cpumask_var_t soft;
};

bool alloc_affinity_masks(struct affinity_masks *affinity);
void free_affinity_masks(struct affinity_masks *affinity);

/* Memory allocation related data for schedule_cpu_rm(). */
struct cpu_rm_data {
    struct affinity_masks affinity;
    const struct scheduler *old_ops;
    void *ppriv_old;
    void *vpriv_old;
    struct sched_resource *sr[];
};

void sched_rm_cpu(unsigned int cpu);
const cpumask_t *sched_get_opt_cpumask(enum sched_gran opt, unsigned int cpu);
void schedule_dump(struct cpupool *c);
struct scheduler *scheduler_get_default(void);
struct scheduler *scheduler_alloc(unsigned int sched_id);
void scheduler_free(struct scheduler *sched);
int cpu_disable_scheduler(unsigned int cpu);
int schedule_cpu_add(unsigned int cpu, struct cpupool *c);
struct cpu_rm_data *alloc_cpu_rm_data(unsigned int cpu, bool aff_alloc);
void free_cpu_rm_data(struct cpu_rm_data *mem, unsigned int cpu);
int schedule_cpu_rm(unsigned int cpu, struct cpu_rm_data *data);
int sched_move_domain(struct domain *d, struct cpupool *c);
void sched_migrate_timers(unsigned int cpu);
struct cpupool *cpupool_get_by_id(unsigned int poolid);
void cpupool_put(struct cpupool *pool);
int cpupool_add_domain(struct domain *d, unsigned int poolid);
void cpupool_rm_domain(struct domain *d);

#endif /* __XEN_SCHED_IF_H__ */