From: William Lee Irwin III <wli@holomorphy.com>
Move the slow paths of wait_on_bit() and wait_on_bit_lock() out of line.
Also uninline wake_up_bit() to reduce the number of callsites generated,
and adjust loop startup in __wait_on_bit_lock() to properly reflect its
usage in the contention case.
Incremental atop the fastcall and wait_on_bit_lock()/test_and_set_bit()
fixes. Successfully tested on x86-64.
Signed-off-by: Andrew Morton <akpm@osdl.org>
---
25-akpm/include/linux/wait.h | 32 +++++---------------------------
25-akpm/kernel/wait.c | 40 ++++++++++++++++++++++++++++++++++++++--
2 files changed, 43 insertions(+), 29 deletions(-)
diff -puN include/linux/wait.h~move-wait-ops-contention-case-completely-out-of-line include/linux/wait.h
--- 25/include/linux/wait.h~move-wait-ops-contention-case-completely-out-of-line Tue Aug 31 14:45:08 2004
+++ 25-akpm/include/linux/wait.h Tue Aug 31 14:45:08 2004
@@ -142,23 +142,11 @@ extern void FASTCALL(__wake_up_sync(wait
void FASTCALL(__wake_up_bit(wait_queue_head_t *, void *, int));
int FASTCALL(__wait_on_bit(wait_queue_head_t *, struct wait_bit_queue *, void *, int, int (*)(void *), unsigned));
int FASTCALL(__wait_on_bit_lock(wait_queue_head_t *, struct wait_bit_queue *, void *, int, int (*)(void *), unsigned));
+void FASTCALL(wake_up_bit(void *, int));
+int FASTCALL(out_of_line_wait_on_bit(void *, int, int (*)(void *), unsigned));
+int FASTCALL(out_of_line_wait_on_bit_lock(void *, int, int (*)(void *), unsigned));
wait_queue_head_t *FASTCALL(bit_waitqueue(void *, int));
-/**
- * wake_up_bit - wake up a waiter on a bit
- * @word: the word being waited on, a kernel virtual address
- * @bit: the bit of the word being waited on
- *
- * There is a standard hashed waitqueue table for generic use. This
- * is the part of the hashtable's accessor API that wakes up waiters
- * on a bit. For instance, if one were to have waiters on a bitflag,
- * one would call wake_up_bit() after clearing the bit.
- */
-static inline void wake_up_bit(void *word, int bit)
-{
- __wake_up_bit(bit_waitqueue(word, bit), word, bit);
-}
-
#define wake_up(x) __wake_up(x, TASK_UNINTERRUPTIBLE | TASK_INTERRUPTIBLE, 1, NULL)
#define wake_up_nr(x, nr) __wake_up(x, TASK_UNINTERRUPTIBLE | TASK_INTERRUPTIBLE, nr, NULL)
#define wake_up_all(x) __wake_up(x, TASK_UNINTERRUPTIBLE | TASK_INTERRUPTIBLE, 0, NULL)
@@ -356,14 +344,9 @@ int wake_bit_function(wait_queue_t *wait
static inline int wait_on_bit(void *word, int bit,
int (*action)(void *), unsigned mode)
{
- DEFINE_WAIT_BIT(q, word, bit);
- wait_queue_head_t *wqh;
-
if (!test_bit(bit, word))
return 0;
-
- wqh = bit_waitqueue(word, bit);
- return __wait_on_bit(wqh, &q, word, bit, action, mode);
+ return out_of_line_wait_on_bit(word, bit, action, mode);
}
/**
@@ -385,14 +368,9 @@ static inline int wait_on_bit(void *word
static inline int wait_on_bit_lock(void *word, int bit,
int (*action)(void *), unsigned mode)
{
- DEFINE_WAIT_BIT(q, word, bit);
- wait_queue_head_t *wqh;
-
if (!test_and_set_bit(bit, word))
return 0;
-
- wqh = bit_waitqueue(word, bit);
- return __wait_on_bit_lock(wqh, &q, word, bit, action, mode);
+ return out_of_line_wait_on_bit_lock(word, bit, action, mode);
}
#endif /* __KERNEL__ */
diff -puN kernel/wait.c~move-wait-ops-contention-case-completely-out-of-line kernel/wait.c
--- 25/kernel/wait.c~move-wait-ops-contention-case-completely-out-of-line Tue Aug 31 14:45:08 2004
+++ 25-akpm/kernel/wait.c Tue Aug 31 14:47:04 2004
@@ -164,24 +164,44 @@ __wait_on_bit(wait_queue_head_t *wq, str
}
EXPORT_SYMBOL(__wait_on_bit);
+int __sched fastcall out_of_line_wait_on_bit(void *word, int bit,
+ int (*action)(void *), unsigned mode)
+{
+ wait_queue_head_t *wq = bit_waitqueue(word, bit);
+ DEFINE_WAIT_BIT(wait, word, bit);
+
+ return __wait_on_bit(wq, &wait, word, bit, action, mode);
+}
+EXPORT_SYMBOL(out_of_line_wait_on_bit);
+
int __sched fastcall
__wait_on_bit_lock(wait_queue_head_t *wq, struct wait_bit_queue *q,
void *word, int bit, int (*action)(void *), unsigned mode)
{
int ret = 0;
- while (test_and_set_bit(bit, word)) {
+ do {
prepare_to_wait_exclusive(wq, &q->wait, mode);
if (test_bit(bit, word)) {
if ((ret = (*action)(word)))
break;
}
- }
+ } while (test_and_set_bit(bit, word));
finish_wait(wq, &q->wait);
return ret;
}
EXPORT_SYMBOL(__wait_on_bit_lock);
+int __sched fastcall out_of_line_wait_on_bit_lock(void *word, int bit,
+ int (*action)(void *), unsigned mode)
+{
+ wait_queue_head_t *wq = bit_waitqueue(word, bit);
+ DEFINE_WAIT_BIT(wait, word, bit);
+
+ return __wait_on_bit_lock(wq, &wait, word, bit, action, mode);
+}
+EXPORT_SYMBOL(out_of_line_wait_on_bit_lock);
+
void fastcall __wake_up_bit(wait_queue_head_t *wq, void *word, int bit)
{
struct wait_bit_key key = __WAIT_BIT_KEY_INITIALIZER(word, bit);
@@ -190,6 +210,22 @@ void fastcall __wake_up_bit(wait_queue_h
}
EXPORT_SYMBOL(__wake_up_bit);
+/**
+ * wake_up_bit - wake up a waiter on a bit
+ * @word: the word being waited on, a kernel virtual address
+ * @bit: the bit of the word being waited on
+ *
+ * There is a standard hashed waitqueue table for generic use. This
+ * is the part of the hashtable's accessor API that wakes up waiters
+ * on a bit. For instance, if one were to have waiters on a bitflag,
+ * one would call wake_up_bit() after clearing the bit.
+ */
+void fastcall wake_up_bit(void *word, int bit)
+{
+ __wake_up_bit(bit_waitqueue(word, bit), word, bit);
+}
+EXPORT_SYMBOL(wake_up_bit);
+
fastcall wait_queue_head_t *bit_waitqueue(void *word, int bit)
{
const int shift = BITS_PER_LONG == 32 ? 5 : 6;
_