On Wed, Apr 28, 2010 at 1:03 PM, Changli Gao <xiaosuo@xxxxxxxxx> wrote: > implement the exclusive wait queue as a LIFO queue > > If the exclusive wait queue is also a LIFO queue as the normal wait queue, the > process who goes to sleep recently, will be woke up first. As its memory is > more likely in cache, we will get better performance. And when there are many > processes waiting on a exclusive wait queue, some of them may not be woke up, > if the others can handle the workload, and it will reduce the load of > the scheduler. > Starve some processes for performance? > Note: before applying this patch, you need my previous patch patched first. > https://patchwork.kernel.org/patch/95600/ > > Signed-off-by: Changli Gao <xiaosuo@xxxxxxxxx> > ---- > fs/eventpoll.c | 3 +-- > include/linux/wait.h | 17 +++++++---------- > kernel/sched.c | 8 ++++---- > kernel/wait.c | 9 +++------ > 4 files changed, 15 insertions(+), 22 deletions(-) > diff --git a/fs/eventpoll.c b/fs/eventpoll.c > index bd056a5..e9b3ebe 100644 > --- a/fs/eventpoll.c > +++ b/fs/eventpoll.c > @@ -1140,8 +1140,7 @@ retry: > * ep_poll_callback() when events will become available. > */ > init_waitqueue_entry(&wait, current); > - wait.flags |= WQ_FLAG_EXCLUSIVE; > - __add_wait_queue(&ep->wq, &wait); > + __add_wait_queue_ex(&ep->wq, &wait); > > for (;;) { > /* > diff --git a/include/linux/wait.h b/include/linux/wait.h > index a48e16b..95c127d 100644 > --- a/include/linux/wait.h > +++ b/include/linux/wait.h > @@ -30,8 +30,6 @@ typedef int (*wait_queue_func_t)(wait_queue_t *wait, unsigned mode, int flags, v > int default_wake_function(wait_queue_t *wait, unsigned mode, int flags, void *key); > > struct __wait_queue { > - unsigned int flags; > -#define WQ_FLAG_EXCLUSIVE 0x01 > void *private; > wait_queue_func_t func; > struct list_head task_list; > @@ -50,6 +48,7 @@ struct wait_bit_queue { > struct __wait_queue_head { > spinlock_t lock; > struct list_head task_list; > + struct list_head task_list_ex; > }; > typedef struct __wait_queue_head wait_queue_head_t; > > @@ -69,7 +68,8 @@ struct task_struct; > > #define __WAIT_QUEUE_HEAD_INITIALIZER(name) { \ > .lock = __SPIN_LOCK_UNLOCKED(name.lock), \ > - .task_list = { &(name).task_list, &(name).task_list } } > + .task_list = { &(name).task_list, &(name).task_list }, \ > + .task_list_ex = { &(name).task_list_ex, &(name).task_list_ex } } > > #define DECLARE_WAIT_QUEUE_HEAD(name) \ > wait_queue_head_t name = __WAIT_QUEUE_HEAD_INITIALIZER(name) > @@ -97,7 +97,6 @@ extern void __init_waitqueue_head(wait_queue_head_t *q, struct lock_class_key *) > > static inline void init_waitqueue_entry(wait_queue_t *q, struct task_struct *p) > { > - q->flags = 0; > q->private = p; > q->func = default_wake_function; > } > @@ -105,14 +104,13 @@ static inline void init_waitqueue_entry(wait_queue_t *q, struct task_struct *p) > static inline void init_waitqueue_func_entry(wait_queue_t *q, > wait_queue_func_t func) > { > - q->flags = 0; > q->private = NULL; > q->func = func; > } > > static inline int waitqueue_active(wait_queue_head_t *q) > { > - return !list_empty(&q->task_list); > + return !list_empty(&q->task_list) || !list_empty(&q->task_list); > } > > extern void add_wait_queue(wait_queue_head_t *q, wait_queue_t *wait); > @@ -127,10 +125,10 @@ static inline void __add_wait_queue(wait_queue_head_t *head, wait_queue_t *new) > /* > * Used for wake-one threads: > */ > -static inline void __add_wait_queue_tail(wait_queue_head_t *head, > +static inline void __add_wait_queue_ex(wait_queue_head_t *head, > wait_queue_t *new) > { > - list_add_tail(&new->task_list, &head->task_list); > + list_add(&new->task_list, &head->task_list_ex); > } > > static inline void __remove_wait_queue(wait_queue_head_t *head, > @@ -409,8 +407,7 @@ do { \ > static inline void add_wait_queue_exclusive_locked(wait_queue_head_t *q, > wait_queue_t * wait) > { > - wait->flags |= WQ_FLAG_EXCLUSIVE; > - __add_wait_queue_tail(q, wait); > + __add_wait_queue_ex(q, wait); > } > > /* > diff --git a/kernel/sched.c b/kernel/sched.c > index be5ab70..59b1534 100644 > --- a/kernel/sched.c > +++ b/kernel/sched.c > @@ -3903,11 +3903,11 @@ static void __wake_up_common(wait_queue_head_t *q, unsigned int mode, > { > wait_queue_t *curr, *next; > > - list_for_each_entry_safe(curr, next, &q->task_list, task_list) { > - unsigned flags = curr->flags; > + list_for_each_entry_safe(curr, next, &q->task_list, task_list) > + curr->func(curr, mode, wake_flags, key); > > - if (curr->func(curr, mode, wake_flags, key) && > - (flags & WQ_FLAG_EXCLUSIVE) && !--nr_exclusive) > + list_for_each_entry_safe(curr, next, &q->task_list_ex, task_list) { > + if (curr->func(curr, mode, wake_flags, key) && !--nr_exclusive) > break; > } > } > diff --git a/kernel/wait.c b/kernel/wait.c > index c4bd3d8..a0559df 100644 > --- a/kernel/wait.c > +++ b/kernel/wait.c > @@ -15,6 +15,7 @@ void __init_waitqueue_head(wait_queue_head_t *q, struct lock_class_key *key) > spin_lock_init(&q->lock); > lockdep_set_class(&q->lock, key); > INIT_LIST_HEAD(&q->task_list); > + INIT_LIST_HEAD(&q->task_list_ex); > } > > EXPORT_SYMBOL(__init_waitqueue_head); > @@ -23,7 +24,6 @@ void add_wait_queue(wait_queue_head_t *q, wait_queue_t *wait) > { > unsigned long flags; > > - wait->flags &= ~WQ_FLAG_EXCLUSIVE; > spin_lock_irqsave(&q->lock, flags); > __add_wait_queue(q, wait); > spin_unlock_irqrestore(&q->lock, flags); > @@ -34,9 +34,8 @@ void add_wait_queue_exclusive(wait_queue_head_t *q, wait_queue_t *wait) > { > unsigned long flags; > > - wait->flags |= WQ_FLAG_EXCLUSIVE; > spin_lock_irqsave(&q->lock, flags); > - __add_wait_queue_tail(q, wait); > + __add_wait_queue_ex(q, wait); > spin_unlock_irqrestore(&q->lock, flags); > } > EXPORT_SYMBOL(add_wait_queue_exclusive); > @@ -69,7 +68,6 @@ prepare_to_wait(wait_queue_head_t *q, wait_queue_t *wait, int state) > { > unsigned long flags; > > - wait->flags &= ~WQ_FLAG_EXCLUSIVE; > spin_lock_irqsave(&q->lock, flags); > if (list_empty(&wait->task_list)) > __add_wait_queue(q, wait); > @@ -83,10 +81,9 @@ prepare_to_wait_exclusive(wait_queue_head_t *q, wait_queue_t *wait, int state) > { > unsigned long flags; > > - wait->flags |= WQ_FLAG_EXCLUSIVE; > spin_lock_irqsave(&q->lock, flags); > if (list_empty(&wait->task_list)) > - __add_wait_queue_tail(q, wait); > + __add_wait_queue_ex(q, wait); > set_current_state(state); > spin_unlock_irqrestore(&q->lock, flags); > } > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
