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[POWERPC] spufs: runqueue simplification 

This is the biggest patch in this series, and it reworks the guts of
the spu scheduler runqueue mechanism:

 - instead of embedding a waitqueue in the runqueue there is now a
   simple doubly-linked list, the actual wakeups happen by reusing
   the stop_wq in the spu context (maybe we should rename it one day)
 - spu_free and spu_prio_wakeup are merged into a single spu_reschedule
   function
 - various functionality is split out into small helpers, and kerneldoc
   comments are added in various places to document what's going on.
 - spu_activate is rewritten into a tight loop by removing test for
   various impossible conditions and using the infrastructure in this
   patch.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Arnd Bergmann <arnd.bergmann@de.ibm.com>
This commit is contained in:
Christoph Hellwig 2007-02-13 21:54:23 +01:00 committed by Arnd Bergmann
parent 8389998ae9
commit 079cdb6161
2 changed files with 95 additions and 69 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

163
arch/powerpc/platforms/cell/spufs/sched.c
View File

@ -49,7 +49,8 @@
#define SPU_BITMAP_SIZE (((MAX_PRIO+BITS_PER_LONG)/BITS_PER_LONG)+1)
struct spu_prio_array {
unsigned long bitmap[SPU_BITMAP_SIZE];
wait_queue_head_t waitq[MAX_PRIO];
struct list_head runq[MAX_PRIO];
spinlock_t runq_lock;
struct list_head active_list[MAX_NUMNODES];
struct mutex active_mutex[MAX_NUMNODES];
};
@ -196,61 +197,91 @@ static int spu_unbind_context(struct spu *spu, struct spu_context *ctx)
return was_active;
}
static inline void spu_add_wq(wait_queue_head_t * wq, wait_queue_t * wait,
int prio)
/**
* spu_add_to_rq - add a context to the runqueue
* @ctx: context to add
*/
static void spu_add_to_rq(struct spu_context *ctx)
{
prepare_to_wait_exclusive(wq, wait, TASK_INTERRUPTIBLE);
set_bit(prio, spu_prio->bitmap);
spin_lock(&spu_prio->runq_lock);
list_add_tail(&ctx->rq, &spu_prio->runq[ctx->prio]);
set_bit(ctx->prio, spu_prio->bitmap);
spin_unlock(&spu_prio->runq_lock);
}
static inline void spu_del_wq(wait_queue_head_t * wq, wait_queue_t * wait,
int prio)
/**
* spu_del_from_rq - remove a context from the runqueue
* @ctx: context to remove
*/
static void spu_del_from_rq(struct spu_context *ctx)
{
u64 flags;
__set_current_state(TASK_RUNNING);
spin_lock_irqsave(&wq->lock, flags);
remove_wait_queue_locked(wq, wait);
if (list_empty(&wq->task_list))
clear_bit(prio, spu_prio->bitmap);
spin_unlock_irqrestore(&wq->lock, flags);
spin_lock(&spu_prio->runq_lock);
list_del_init(&ctx->rq);
if (list_empty(&spu_prio->runq[ctx->prio]))
clear_bit(ctx->prio, spu_prio->bitmap);
spin_unlock(&spu_prio->runq_lock);
}
static void spu_prio_wait(struct spu_context *ctx, u64 flags)
/**
* spu_grab_context - remove one context from the runqueue
* @prio: priority of the context to be removed
*
* This function removes one context from the runqueue for priority @prio.
* If there is more than one context with the given priority the first
* task on the runqueue will be taken.
*
* Returns the spu_context it just removed.
*
* Must be called with spu_prio->runq_lock held.
*/
static struct spu_context *spu_grab_context(int prio)
{
struct list_head *rq = &spu_prio->runq[prio];
if (list_empty(rq))
return NULL;
return list_entry(rq->next, struct spu_context, rq);
}
static void spu_prio_wait(struct spu_context *ctx)
{
int prio = ctx->prio;
wait_queue_head_t *wq = &spu_prio->waitq[prio];
DEFINE_WAIT(wait);
if (ctx->spu)
return;
spu_add_wq(wq, &wait, prio);
prepare_to_wait_exclusive(&ctx->stop_wq, &wait, TASK_INTERRUPTIBLE);
if (!signal_pending(current)) {
mutex_unlock(&ctx->state_mutex);
pr_debug("%s: pid=%d prio=%d\n", __FUNCTION__,
current->pid, current->prio);
schedule();
mutex_lock(&ctx->state_mutex);
}
spu_del_wq(wq, &wait, prio);
__set_current_state(TASK_RUNNING);
remove_wait_queue(&ctx->stop_wq, &wait);
}
static void spu_prio_wakeup(void)
/**
* spu_reschedule - try to find a runnable context for a spu
* @spu: spu available
*
* This function is called whenever a spu becomes idle. It looks for the
* most suitable runnable spu context and schedules it for execution.
*/
static void spu_reschedule(struct spu *spu)
{
int best = sched_find_first_bit(spu_prio->bitmap);
int best;
spu_free(spu);
spin_lock(&spu_prio->runq_lock);
best = sched_find_first_bit(spu_prio->bitmap);
if (best < MAX_PRIO) {
wait_queue_head_t *wq = &spu_prio->waitq[best];
wake_up_interruptible_nr(wq, 1);
struct spu_context *ctx = spu_grab_context(best);
if (ctx)
wake_up(&ctx->stop_wq);
}
spin_unlock(&spu_prio->runq_lock);
}
static struct spu *spu_get_idle(struct spu_context *ctx, u64 flags)
static struct spu *spu_get_idle(struct spu_context *ctx)
{
struct spu *spu = NULL;
int node = cpu_to_node(raw_smp_processor_id());
@ -267,15 +298,6 @@ static struct spu *spu_get_idle(struct spu_context *ctx, u64 flags)
return spu;
}
static inline struct spu *spu_get(struct spu_context *ctx, u64 flags)
{
/* Future: spu_get_idle() if possible,
* otherwise try to preempt an active
* context.
*/
return spu_get_idle(ctx, flags);
}
/* The three externally callable interfaces
* for the scheduler begin here.
*
@ -284,32 +306,36 @@ static inline struct spu *spu_get(struct spu_context *ctx, u64 flags)
* spu_yield - yield an SPU if others are waiting.
*/
/**
* spu_activate - find a free spu for a context and execute it
* @ctx: spu context to schedule
* @flags: flags (currently ignored)
*
* Tries to find a free spu to run @ctx. If no free spu is availble
* add the context to the runqueue so it gets woken up once an spu
* is available.
*/
int spu_activate(struct spu_context *ctx, u64 flags)
{
struct spu *spu;
int ret = 0;
for (;;) {
if (ctx->spu)
return 0;
spu = spu_get(ctx, flags);
if (spu != NULL) {
if (ctx->spu != NULL) {
spu_free(spu);
spu_prio_wakeup();
break;
}
if (ctx->spu)
return 0;
do {
struct spu *spu;
spu = spu_get_idle(ctx);
if (spu) {
spu_bind_context(spu, ctx);
break;
return 0;
}
spu_prio_wait(ctx, flags);
if (signal_pending(current)) {
ret = -ERESTARTSYS;
spu_prio_wakeup();
break;
}
}
return ret;
spu_add_to_rq(ctx);
spu_prio_wait(ctx);
spu_del_from_rq(ctx);
} while (!signal_pending(current));
return -ERESTARTSYS;
}
void spu_deactivate(struct spu_context *ctx)
@ -321,10 +347,8 @@ void spu_deactivate(struct spu_context *ctx)
if (!spu)
return;
was_active = spu_unbind_context(spu, ctx);
if (was_active) {
spu_free(spu);
spu_prio_wakeup();
}
if (was_active)
spu_reschedule(spu);
}
void spu_yield(struct spu_context *ctx)
@ -359,7 +383,7 @@ int __init spu_sched_init(void)
return 1;
}
for (i = 0; i < MAX_PRIO; i++) {
init_waitqueue_head(&spu_prio->waitq[i]);
INIT_LIST_HEAD(&spu_prio->runq[i]);
__clear_bit(i, spu_prio->bitmap);
}
__set_bit(MAX_PRIO, spu_prio->bitmap);
@ -367,6 +391,7 @@ int __init spu_sched_init(void)
mutex_init(&spu_prio->active_mutex[i]);
INIT_LIST_HEAD(&spu_prio->active_list[i]);
}
spin_lock_init(&spu_prio->runq_lock);
return 0;
}

1
arch/powerpc/platforms/cell/spufs/spufs.h
View File

@ -76,6 +76,7 @@ struct spu_context {
struct spu_gang *gang;
/* scheduler fields */
struct list_head rq;
int prio;
};