proc_wakeup() replaces schedule_scp()

[akaros.git] / kern / src / schedule.c

/* Copyright (c) 2009, 2012 The Regents of the University of California
 * Barret Rhoden <brho@cs.berkeley.edu>
 * See LICENSE for details.
 *
 * Scheduling and dispatching. */

#ifdef __SHARC__
#pragma nosharc
#endif

#include <schedule.h>
#include <process.h>
#include <monitor.h>
#include <stdio.h>
#include <assert.h>
#include <atomic.h>
#include <smp.h>
#include <manager.h>
#include <alarm.h>
#include <sys/queue.h>

/* Process Lists.  'unrunnable' is a holding list for SCPs that are running or
 * waiting or otherwise not considered for sched decisions. */
struct proc_list unrunnable_scps = TAILQ_HEAD_INITIALIZER(unrunnable_scps);
struct proc_list runnable_scps = TAILQ_HEAD_INITIALIZER(runnable_scps);
struct proc_list all_mcps = TAILQ_HEAD_INITIALIZER(all_mcps);
spinlock_t sched_lock = SPINLOCK_INITIALIZER;

// This could be useful for making scheduling decisions.  
/* Physical coremap: each index is a physical core id, with a proc ptr for
 * whoever *should be or is* running.  Very similar to current, which is what
 * process is *really* running there. */
struct proc *pcoremap[MAX_NUM_CPUS];

/* Tracks which cores are idle, similar to the vcoremap.  Each value is the
 * physical coreid of an unallocated core. */
spinlock_t idle_lock = SPINLOCK_INITIALIZER;
uint32_t idlecoremap[MAX_NUM_CPUS];
uint32_t num_idlecores = 0;
uint32_t num_mgmtcores = 1;

/* Helper, defined below */
static void __core_request(struct proc *p);
static void __put_idle_cores(uint32_t *pc_arr, uint32_t num);
static void add_to_list(struct proc *p, struct proc_list *list);
static void remove_from_list(struct proc *p, struct proc_list *list);
static void switch_lists(struct proc *p, struct proc_list *old,
                         struct proc_list *new);

/* Alarm struct, for our example 'timer tick' */
struct alarm_waiter ksched_waiter;

#define TIMER_TICK_USEC 10000   /* 10msec */

/* Helper: Sets up a timer tick on the calling core to go off 10 msec from now.
 * This assumes the calling core is an LL core, etc. */
static void set_ksched_alarm(void)
{
        set_awaiter_rel(&ksched_waiter, TIMER_TICK_USEC);
        set_alarm(&per_cpu_info[core_id()].tchain, &ksched_waiter);
}

/* Kmsg, to run the scheduler tick (not in interrupt context) and reset the
 * alarm.  Note that interrupts will be disabled, but this is not the same as
 * interrupt context.  We're a routine kmsg, which means the core is in a
 * quiescent state. */
static void __ksched_tick(struct trapframe *tf, uint32_t srcid, long a0,
                          long a1, long a2)
{
        /* TODO: imagine doing some accounting here */
        schedule();
        /* Set our alarm to go off, incrementing from our last tick (instead of
         * setting it relative to now, since some time has passed since the alarm
         * first went off.  Note, this may be now or in the past! */
        set_awaiter_inc(&ksched_waiter, TIMER_TICK_USEC);
        set_alarm(&per_cpu_info[core_id()].tchain, &ksched_waiter);
}

/* Interrupt/alarm handler: tells our core to run the scheduler (out of
 * interrupt context). */
static void __kalarm(struct alarm_waiter *waiter)
{
        send_kernel_message(core_id(), __ksched_tick, 0, 0, 0, KMSG_ROUTINE);
}

void schedule_init(void)
{
        assert(!core_id());             /* want the alarm on core0 for now */
        init_awaiter(&ksched_waiter, __kalarm);
        set_ksched_alarm();
        /* Ghetto old idle core init */
        /* Init idle cores. Core 0 is the management core. */
        spin_lock(&idle_lock);
#ifdef __CONFIG_DISABLE_SMT__
        /* assumes core0 is the only management core (NIC and monitor functionality
         * are run there too.  it just adds the odd cores to the idlecoremap */
        assert(!(num_cpus % 2));
        // TODO: consider checking x86 for machines that actually hyperthread
        num_idlecores = num_cpus >> 1;
 #ifdef __CONFIG_ARSC_SERVER__
        // Dedicate one core (core 2) to sysserver, might be able to share wit NIC
        num_mgmtcores++;
        assert(num_cpus >= num_mgmtcores);
        send_kernel_message(2, (amr_t)arsc_server, 0,0,0, KMSG_ROUTINE);
 #endif
        for (int i = 0; i < num_idlecores; i++)
                idlecoremap[i] = (i * 2) + 1;
#else
        // __CONFIG_DISABLE_SMT__
        #ifdef __CONFIG_NETWORKING__
        num_mgmtcores++; // Next core is dedicated to the NIC
        assert(num_cpus >= num_mgmtcores);
        #endif
        #ifdef __CONFIG_APPSERVER__
        #ifdef __CONFIG_DEDICATED_MONITOR__
        num_mgmtcores++; // Next core dedicated to running the kernel monitor
        assert(num_cpus >= num_mgmtcores);
        // Need to subtract 1 from the num_mgmtcores # to get the cores index
        send_kernel_message(num_mgmtcores-1, (amr_t)monitor, 0,0,0, KMSG_ROUTINE);
        #endif
        #endif
 #ifdef __CONFIG_ARSC_SERVER__
        // Dedicate one core (core 2) to sysserver, might be able to share with NIC
        num_mgmtcores++;
        assert(num_cpus >= num_mgmtcores);
        send_kernel_message(num_mgmtcores-1, (amr_t)arsc_server, 0,0,0, KMSG_ROUTINE);
 #endif
        num_idlecores = num_cpus - num_mgmtcores;
        for (int i = 0; i < num_idlecores; i++)
                idlecoremap[i] = i + num_mgmtcores;
#endif /* __CONFIG_DISABLE_SMT__ */
        spin_unlock(&idle_lock);
        return;
}

/* Round-robins on whatever list it's on */
static void add_to_list(struct proc *p, struct proc_list *new)
{
        TAILQ_INSERT_TAIL(new, p, ksched_data.proc_link);
        p->ksched_data.cur_list = new;
}

static void remove_from_list(struct proc *p, struct proc_list *old)
{
        assert(p->ksched_data.cur_list == old);
        TAILQ_REMOVE(old, p, ksched_data.proc_link);
}

static void switch_lists(struct proc *p, struct proc_list *old,
                         struct proc_list *new)
{
        remove_from_list(p, old);
        add_to_list(p, new);
}

static void __remove_from_any_list(struct proc *p)
{
        if (p->ksched_data.cur_list)
                TAILQ_REMOVE(p->ksched_data.cur_list, p, ksched_data.proc_link);
}

/* Removes from whatever list p is on */
static void remove_from_any_list(struct proc *p)
{
        assert(p->ksched_data.cur_list);
        TAILQ_REMOVE(p->ksched_data.cur_list, p, ksched_data.proc_link);
}

void register_proc(struct proc *p)
{
        /* one ref for the proc's existence, cradle-to-grave */
        proc_incref(p, 1);      /* need at least this OR the 'one for existing' */
        spin_lock(&sched_lock);
        add_to_list(p, &unrunnable_scps);
        spin_unlock(&sched_lock);
}

/* Returns 0 if it succeeded, an error code otherwise. */
int proc_change_to_m(struct proc *p)
{
        int retval;
        spin_lock(&sched_lock);
        /* Should only be necessary to lock around the change_to_m call.  It's
         * definitely necessary to hold the sched lock the whole time - need to
         * atomically change the proc's state and have the ksched take action (and
         * not squeeze a proc_destroy in there or something). */
        spin_lock(&p->proc_lock);
        retval = __proc_change_to_m(p);
        spin_unlock(&p->proc_lock);
        if (retval) {
                /* Failed for some reason. */
                spin_unlock(&sched_lock);
                return retval;
        }
        /* Catch user bugs */
        if (!p->procdata->res_req[RES_CORES].amt_wanted) {
                printk("[kernel] process needs to specify amt_wanted\n");
                p->procdata->res_req[RES_CORES].amt_wanted = 1;
        }
        /* For now, this should only ever be called on an unrunnable.  It's
         * probably a bug, at this stage in development, to do o/w. */
        remove_from_list(p, &unrunnable_scps);
        //remove_from_any_list(p);      /* ^^ instead of this */
        add_to_list(p, &all_mcps);
        spin_unlock(&sched_lock);
        //poke_ksched(p, RES_CORES);
        return retval;
}

/* Makes sure p is runnable.  Callers may spam this, so it needs to handle
 * repeated calls for the same event.  Callers include event delivery, SCP
 * yield, and new SCPs.  Most every scheduler should do something like this -
 * grab whatever lock you have, then call the proc helper. */
void proc_wakeup(struct proc *p)
{
        spin_lock(&sched_lock);
        /* will trigger one of the __sched_.cp_wakeup()s */
        __proc_wakeup(p);
        spin_unlock(&sched_lock);
}

/* Destroys the given process.  This may be called from another process, a light
 * kernel thread (no real process context), asynchronously/cross-core, or from
 * the process on its own core.
 *
 * An external, edible ref is passed in.  when we return and they decref,
 * __proc_free will be called */
void proc_destroy(struct proc *p)
{
        uint32_t nr_cores_revoked = 0;
        spin_lock(&sched_lock);
        spin_lock(&p->proc_lock);
        /* storage for pc_arr is alloced at decl, which is after grabbing the lock*/
        uint32_t pc_arr[p->procinfo->num_vcores];
        /* If this returns true, it means we successfully destroyed the proc */
        if (__proc_destroy(p, pc_arr, &nr_cores_revoked)) {
                /* Do our cleanup.  note that proc_free won't run since we have an
                 * external reference, passed in */

                /* Remove from whatever list we are on */
                remove_from_any_list(p);
                /* Drop the cradle-to-the-grave reference, jet-li */
                proc_decref(p);
                /* Put the cores back on the idlecore map.  For future changes, be
                 * careful with the idle_lock.  It's safe to call this here or outside
                 * the sched lock (for now). */
                if (nr_cores_revoked) 
                        put_idle_cores(pc_arr, nr_cores_revoked);
        }
        spin_unlock(&p->proc_lock);
        spin_unlock(&sched_lock);
}

/* mgmt/LL cores should call this to schedule the calling core and give it to an
 * SCP.  will also prune the dead SCPs from the list.  hold the lock before
 * calling.  returns TRUE if it scheduled a proc. */
static bool __schedule_scp(void)
{
        struct proc *p;
        uint32_t pcoreid = core_id();
        struct per_cpu_info *pcpui = &per_cpu_info[pcoreid];
        int8_t state = 0;
        /* if there are any runnables, run them here and put any currently running
         * SCP on the tail of the runnable queue. */
        if ((p = TAILQ_FIRST(&runnable_scps))) {
                /* protect owning proc, cur_tf, etc.  note this nests with the
                 * calls in proc_yield_s */
                disable_irqsave(&state);
                /* someone is currently running, dequeue them */
                if (pcpui->owning_proc) {
                        printd("Descheduled %d in favor of %d\n", pcpui->owning_proc->pid,
                               p->pid);
                        /* locking just to be safe */
                        spin_lock(&p->proc_lock);
                        __proc_set_state(pcpui->owning_proc, PROC_RUNNABLE_S);
                        __proc_save_context_s(pcpui->owning_proc, pcpui->cur_tf);
                        spin_unlock(&p->proc_lock);
                        /* round-robin the SCPs (inserts at the end of the queue) */
                        switch_lists(pcpui->owning_proc, &unrunnable_scps, &runnable_scps);
                        clear_owning_proc(pcoreid);
                        /* Note we abandon core.  It's not strictly necessary.  If
                         * we didn't, the TLB would still be loaded with the old
                         * one, til we proc_run_s, and the various paths in
                         * proc_run_s would pick it up.  This way is a bit safer for
                         * future changes, but has an extra (empty) TLB flush.  */
                        abandon_core();
                } 
                /* Run the new proc */
                switch_lists(p, &runnable_scps, &unrunnable_scps);
                printd("PID of the SCP i'm running: %d\n", p->pid);
                proc_run_s(p);  /* gives it core we're running on */
                enable_irqsave(&state);
                return TRUE;
        }
        return FALSE;
}

/* Something has changed, and for whatever reason the scheduler should
 * reevaluate things. 
 *
 * Don't call this from interrupt context (grabs proclocks). */
void schedule(void)
{
        struct proc *p, *temp;
        spin_lock(&sched_lock);
        /* trivially try to handle the needs of all our MCPS.  smarter schedulers
         * would do something other than FCFS */
        TAILQ_FOREACH_SAFE(p, &all_mcps, ksched_data.proc_link, temp) {
                printd("Ksched has MCP %08p (%d)\n", p, p->pid);
                if (!num_idlecores)
                        break;
                /* TODO: might use amt_wanted as a proxy.  right now, they have
                 * amt_wanted == 1, even though they are waiting.
                 * TODO: this is RACY too - just like with DYING. */
                if (p->state == PROC_WAITING)
                        continue;
                __core_request(p);
        }
        if (management_core())
                __schedule_scp();
        spin_unlock(&sched_lock);
}

/* A process is asking the ksched to look at its resource desires.  The
 * scheduler is free to ignore this, for its own reasons, so long as it
 * eventually gets around to looking at resource desires. */
void poke_ksched(struct proc *p, int res_type)
{
        /* TODO: probably want something to trigger all res_types */
        spin_lock(&sched_lock);
        switch (res_type) {
                case RES_CORES:
                        /* ignore core requests from non-mcps (note we have races if we ever
                         * allow procs to switch back). */
                        if (!__proc_is_mcp(p))
                                break;
                        __core_request(p);
                        break;
                default:
                        break;
        }
        spin_unlock(&sched_lock);
}

/* ksched callbacks.  p just woke up, is unlocked, and the ksched lock is held */
void __sched_mcp_wakeup(struct proc *p)
{
        /* the essence of poke_ksched for RES_CORES */
        __core_request(p);
}

/* ksched callbacks.  p just woke up, is unlocked, and the ksched lock is held */
void __sched_scp_wakeup(struct proc *p)
{
        /* might not be on a list if it is new.  o/w, it should be unrunnable */
        __remove_from_any_list(p);
        add_to_list(p, &runnable_scps);
}

/* The calling cpu/core has nothing to do and plans to idle/halt.  This is an
 * opportunity to pick the nature of that halting (low power state, etc), or
 * provide some other work (_Ss on LL cores).  Note that interrupts are
 * disabled, and if you return, the core will cpu_halt(). */
void cpu_bored(void)
{
        bool new_proc = FALSE;
        if (!management_core())
                return;
        spin_lock(&sched_lock);
        new_proc = __schedule_scp();
        spin_unlock(&sched_lock);
        /* if we just scheduled a proc, we need to manually restart it, instead of
         * returning.  if we return, the core will halt. */
        if (new_proc) {
                proc_restartcore();
                assert(0);
        }
        /* Could drop into the monitor if there are no processes at all.  For now,
         * the 'call of the giraffe' suffices. */
}

/* Helper function to return a core to the idlemap.  It causes some more lock
 * acquisitions (like in a for loop), but it's a little easier.  Plus, one day
 * we might be able to do this without locks (for the putting).
 *
 * This is a trigger, telling us we have more cores.  We could/should make a
 * scheduling decision (or at least plan to). */
void put_idle_core(uint32_t coreid)
{
        spin_lock(&idle_lock);
        idlecoremap[num_idlecores++] = coreid;
        spin_unlock(&idle_lock);
}

/* Helper for put_idle and core_req. */
static void __put_idle_cores(uint32_t *pc_arr, uint32_t num)
{
        spin_lock(&idle_lock);
        for (int i = 0; i < num; i++)
                idlecoremap[num_idlecores++] = pc_arr[i];
        spin_unlock(&idle_lock);
}

/* Bulk interface for put_idle */
void put_idle_cores(uint32_t *pc_arr, uint32_t num)
{
        /* could trigger a sched decision here */
        __put_idle_cores(pc_arr, num);
}

/* Available resources changed (plus or minus).  Some parts of the kernel may
 * call this if a particular resource that is 'quantity-based' changes.  Things
 * like available RAM to processes, bandwidth, etc.  Cores would probably be
 * inappropriate, since we need to know which specific core is now free. */
void avail_res_changed(int res_type, long change)
{
        printk("[kernel] ksched doesn't track any resources yet!\n");
}

/* Normally it'll be the max number of CG cores ever */
uint32_t max_vcores(struct proc *p)
{
#ifdef __CONFIG_DISABLE_SMT__
        return num_cpus >> 1;
#else
        return MAX(1, num_cpus - num_mgmtcores);
#endif /* __CONFIG_DISABLE_SMT__ */
}

/* Ghetto helper, just hands out up to 'amt_new' cores (no sense of locality or
 * anything) */
static uint32_t get_idle_cores(struct proc *p, uint32_t *pc_arr,
                               uint32_t amt_new)
{
        uint32_t num_granted = 0;
        spin_lock(&idle_lock);
        for (int i = 0; i < num_idlecores && i < amt_new; i++) {
                /* grab the last one on the list */
                pc_arr[i] = idlecoremap[num_idlecores - 1];
                num_idlecores--;
                num_granted++;
        }
        spin_unlock(&idle_lock);
        return num_granted;
}

/* This deals with a request for more cores.  The request is already stored in
 * the proc's amt_wanted (it is compared to amt_granted). */
static void __core_request(struct proc *p)
{
        uint32_t num_granted, amt_wanted, amt_granted;
        uint32_t corelist[num_cpus];

        /* TODO: consider copy-in for amt_wanted too. */
        amt_wanted = p->procdata->res_req[RES_CORES].amt_wanted;
        amt_granted = p->procinfo->res_grant[RES_CORES];

        /* Help them out - if they ask for something impossible, give them 1 so they
         * can make some progress. (this is racy). */
        if (amt_wanted > p->procinfo->max_vcores) {
                p->procdata->res_req[RES_CORES].amt_wanted = 1;
        }
        /* if they are satisfied, we're done.  There's a slight chance they have
         * cores, but they aren't running (sched gave them cores while they were
         * yielding, and now we see them on the run queue). */
        if (amt_wanted <= amt_granted)
                return;
        /* Otherwise, see what they want, and try to give out as many as possible.
         * Current models are simple - it's just a raw number of cores, and we just
         * give out what we can. */
        num_granted = get_idle_cores(p, corelist, amt_wanted - amt_granted);
        /* Now, actually give them out */
        if (num_granted) {
                /* give them the cores.  this will start up the extras if RUNNING_M. */
                spin_lock(&p->proc_lock);
                /* if they fail, it is because they are WAITING or DYING.  we could give
                 * the cores to another proc or whatever.  for the current type of
                 * ksched, we'll just put them back on the pile and return.  Note, the
                 * ksched could check the states after locking, but it isn't necessary:
                 * just need to check at some point in the ksched loop. */
                if (__proc_give_cores(p, corelist, num_granted)) {
                        __put_idle_cores(corelist, num_granted);
                } else {
                        /* at some point after giving cores, call proc_run_m() (harmless on
                         * RUNNING_Ms).  You can give small groups of cores, then run them
                         * (which is more efficient than interleaving runs with the gives
                         * for bulk preempted processes). */
                        __proc_run_m(p);
                }
                spin_unlock(&p->proc_lock);
        }
}

/************** Debugging **************/
void sched_diag(void)
{
        struct proc *p;
        spin_lock(&sched_lock);
        TAILQ_FOREACH(p, &runnable_scps, ksched_data.proc_link)
                printk("Runnable _S PID: %d\n", p->pid);
        TAILQ_FOREACH(p, &unrunnable_scps, ksched_data.proc_link)
                printk("Unrunnable _S PID: %d\n", p->pid);
        TAILQ_FOREACH(p, &all_mcps, ksched_data.proc_link)
                printk("MCP PID: %d\n", p->pid);
        spin_unlock(&sched_lock);
        return;
}

void print_idlecoremap(void)
{
        spin_lock(&idle_lock);
        printk("There are %d idle cores.\n", num_idlecores);
        for (int i = 0; i < num_idlecores; i++)
                printk("idlecoremap[%d] = %d\n", i, idlecoremap[i]);
        spin_unlock(&idle_lock);
}

void print_resources(struct proc *p)
{
        printk("--------------------\n");
        printk("PID: %d\n", p->pid);
        printk("--------------------\n");
        for (int i = 0; i < MAX_NUM_RESOURCES; i++)
                printk("Res type: %02d, amt wanted: %08d, amt granted: %08d\n", i,
                       p->procdata->res_req[i].amt_wanted, p->procinfo->res_grant[i]);
}

void print_all_resources(void)
{
        /* Hash helper */
        void __print_resources(void *item)
        {
                print_resources((struct proc*)item);
        }
        spin_lock(&pid_hash_lock);
        hash_for_each(pid_hash, __print_resources);
        spin_unlock(&pid_hash_lock);
}