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SubjectRe: [0/3] filtered wakeups respun
On Tue, May 04, 2004 at 11:06:12PM -0700, William Lee Irwin III wrote:
> Same machine/etc. as before, except this time, ext3 instead of ext2.
> ext3 shows noise-level differences in raw throughputs with large
> reductions in cpu overhead, mostly on the read side.

Precisely the same filtered wakeups for pages as before. Drop in a
fresh wakeup primitive that uses a key to discriminate between the
waiters for different objects on a hashed waitqueue, and make the
page waiting functions use it.


-- wli


Index: wake-2.6.6-rc3-mm1/include/linux/wait.h
===================================================================
--- wake-2.6.6-rc3-mm1.orig/include/linux/wait.h 2004-04-03 19:37:07.000000000 -0800
+++ wake-2.6.6-rc3-mm1/include/linux/wait.h 2004-05-04 13:16:00.000000000 -0700
@@ -28,6 +28,11 @@
struct list_head task_list;
};

+struct filtered_wait_queue {
+ void *key;
+ wait_queue_t wait;
+};
+
struct __wait_queue_head {
spinlock_t lock;
struct list_head task_list;
@@ -104,6 +109,7 @@
list_del(&old->task_list);
}

+void FASTCALL(wake_up_filtered(wait_queue_head_t *, void *));
extern void FASTCALL(__wake_up(wait_queue_head_t *q, unsigned int mode, int nr));
extern void FASTCALL(__wake_up_locked(wait_queue_head_t *q, unsigned int mode));
extern void FASTCALL(__wake_up_sync(wait_queue_head_t *q, unsigned int mode, int nr));
@@ -257,6 +263,16 @@
wait->func = autoremove_wake_function; \
INIT_LIST_HEAD(&wait->task_list); \
} while (0)
+
+#define DEFINE_FILTERED_WAIT(name, p) \
+ struct filtered_wait_queue name = { \
+ .key = p, \
+ .wait = { \
+ .task = current, \
+ .func = autoremove_wake_function, \
+ .task_list = LIST_HEAD_INIT(name.wait.task_list),\
+ }, \
+ }

#endif /* __KERNEL__ */

Index: wake-2.6.6-rc3-mm1/kernel/sched.c
===================================================================
--- wake-2.6.6-rc3-mm1.orig/kernel/sched.c 2004-04-30 15:06:49.000000000 -0700
+++ wake-2.6.6-rc3-mm1/kernel/sched.c 2004-05-04 13:16:00.000000000 -0700
@@ -2518,6 +2518,19 @@
}
}

+void fastcall wake_up_filtered(wait_queue_head_t *q, void *key)
+{
+ unsigned long flags;
+ unsigned int mode = TASK_UNINTERRUPTIBLE | TASK_INTERRUPTIBLE;
+ struct filtered_wait_queue *wait, *save;
+ spin_lock_irqsave(&q->lock, flags);
+ list_for_each_entry_safe(wait, save, &q->task_list, wait.task_list) {
+ if (wait->key == key)
+ wait->wait.func(&wait->wait, mode, 0);
+ }
+ spin_unlock_irqrestore(&q->lock, flags);
+}
+
/**
* __wake_up - wake up threads blocked on a waitqueue.
* @q: the waitqueue
Index: wake-2.6.6-rc3-mm1/mm/filemap.c
===================================================================
--- wake-2.6.6-rc3-mm1.orig/mm/filemap.c 2004-04-30 15:06:49.000000000 -0700
+++ wake-2.6.6-rc3-mm1/mm/filemap.c 2004-05-04 13:16:00.000000000 -0700
@@ -307,16 +307,16 @@
void fastcall wait_on_page_bit(struct page *page, int bit_nr)
{
wait_queue_head_t *waitqueue = page_waitqueue(page);
- DEFINE_WAIT(wait);
+ DEFINE_FILTERED_WAIT(wait, page);

do {
- prepare_to_wait(waitqueue, &wait, TASK_UNINTERRUPTIBLE);
+ prepare_to_wait(waitqueue, &wait.wait, TASK_UNINTERRUPTIBLE);
if (test_bit(bit_nr, &page->flags)) {
sync_page(page);
io_schedule();
}
} while (test_bit(bit_nr, &page->flags));
- finish_wait(waitqueue, &wait);
+ finish_wait(waitqueue, &wait.wait);
}

EXPORT_SYMBOL(wait_on_page_bit);
@@ -344,7 +344,7 @@
BUG();
smp_mb__after_clear_bit();
if (waitqueue_active(waitqueue))
- wake_up_all(waitqueue);
+ wake_up_filtered(waitqueue, page);
}

EXPORT_SYMBOL(unlock_page);
@@ -363,7 +363,7 @@
smp_mb__after_clear_bit();
}
if (waitqueue_active(waitqueue))
- wake_up_all(waitqueue);
+ wake_up_filtered(waitqueue, page);
}

EXPORT_SYMBOL(end_page_writeback);
@@ -379,16 +379,16 @@
void fastcall __lock_page(struct page *page)
{
wait_queue_head_t *wqh = page_waitqueue(page);
- DEFINE_WAIT(wait);
+ DEFINE_FILTERED_WAIT(wait, page);

while (TestSetPageLocked(page)) {
- prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
+ prepare_to_wait(wqh, &wait.wait, TASK_UNINTERRUPTIBLE);
if (PageLocked(page)) {
sync_page(page);
io_schedule();
}
}
- finish_wait(wqh, &wait);
+ finish_wait(wqh, &wait.wait);
}

EXPORT_SYMBOL(__lock_page);
-
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