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authorLinus Torvalds <torvalds@linux-foundation.org>2011-05-19 14:15:29 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2011-05-19 14:15:29 -0700
commite66eed651fd18a961f11cda62f3b5286c8cc4f9f (patch)
tree0b86980050e63623b103f1b6378aa3c457f63e87
parent75d65a425c0163d3ec476ddc12b51087217a070c (diff)
list: remove prefetching from regular list iterators
This is removes the use of software prefetching from the regular list iterators. We don't want it. If you do want to prefetch in some iterator of yours, go right ahead. Just don't expect the iterator to do it, since normally the downsides are bigger than the upsides. It also replaces <linux/prefetch.h> with <linux/const.h>, because the use of LIST_POISON ends up needing it. <linux/poison.h> is sadly not self-contained, and including prefetch.h just happened to hide that. Suggested by David Miller (networking has a lot of regular lists that are often empty or a single entry, and prefetching is not going to do anything but add useless instructions). Acked-by: Ingo Molnar <mingo@elte.hu> Acked-by: David S. Miller <davem@davemloft.net> Cc: linux-arch@vger.kernel.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--include/linux/list.h26
-rw-r--r--include/linux/rculist.h6
2 files changed, 14 insertions, 18 deletions
diff --git a/include/linux/list.h b/include/linux/list.h
index 9ac11148e037..cc6d2aa6b415 100644
--- a/include/linux/list.h
+++ b/include/linux/list.h
@@ -4,7 +4,7 @@
#include <linux/types.h>
#include <linux/stddef.h>
#include <linux/poison.h>
-#include <linux/prefetch.h>
+#include <linux/const.h>
/*
* Simple doubly linked list implementation.
@@ -367,18 +367,15 @@ static inline void list_splice_tail_init(struct list_head *list,
* @head: the head for your list.
*/
#define list_for_each(pos, head) \
- for (pos = (head)->next; prefetch(pos->next), pos != (head); \
- pos = pos->next)
+ for (pos = (head)->next; pos != (head); pos = pos->next)
/**
* __list_for_each - iterate over a list
* @pos: the &struct list_head to use as a loop cursor.
* @head: the head for your list.
*
- * This variant differs from list_for_each() in that it's the
- * simplest possible list iteration code, no prefetching is done.
- * Use this for code that knows the list to be very short (empty
- * or 1 entry) most of the time.
+ * This variant doesn't differ from list_for_each() any more.
+ * We don't do prefetching in either case.
*/
#define __list_for_each(pos, head) \
for (pos = (head)->next; pos != (head); pos = pos->next)
@@ -389,8 +386,7 @@ static inline void list_splice_tail_init(struct list_head *list,
* @head: the head for your list.
*/
#define list_for_each_prev(pos, head) \
- for (pos = (head)->prev; prefetch(pos->prev), pos != (head); \
- pos = pos->prev)
+ for (pos = (head)->prev; pos != (head); pos = pos->prev)
/**
* list_for_each_safe - iterate over a list safe against removal of list entry
@@ -410,7 +406,7 @@ static inline void list_splice_tail_init(struct list_head *list,
*/
#define list_for_each_prev_safe(pos, n, head) \
for (pos = (head)->prev, n = pos->prev; \
- prefetch(pos->prev), pos != (head); \
+ pos != (head); \
pos = n, n = pos->prev)
/**
@@ -421,7 +417,7 @@ static inline void list_splice_tail_init(struct list_head *list,
*/
#define list_for_each_entry(pos, head, member) \
for (pos = list_entry((head)->next, typeof(*pos), member); \
- prefetch(pos->member.next), &pos->member != (head); \
+ &pos->member != (head); \
pos = list_entry(pos->member.next, typeof(*pos), member))
/**
@@ -432,7 +428,7 @@ static inline void list_splice_tail_init(struct list_head *list,
*/
#define list_for_each_entry_reverse(pos, head, member) \
for (pos = list_entry((head)->prev, typeof(*pos), member); \
- prefetch(pos->member.prev), &pos->member != (head); \
+ &pos->member != (head); \
pos = list_entry(pos->member.prev, typeof(*pos), member))
/**
@@ -457,7 +453,7 @@ static inline void list_splice_tail_init(struct list_head *list,
*/
#define list_for_each_entry_continue(pos, head, member) \
for (pos = list_entry(pos->member.next, typeof(*pos), member); \
- prefetch(pos->member.next), &pos->member != (head); \
+ &pos->member != (head); \
pos = list_entry(pos->member.next, typeof(*pos), member))
/**
@@ -471,7 +467,7 @@ static inline void list_splice_tail_init(struct list_head *list,
*/
#define list_for_each_entry_continue_reverse(pos, head, member) \
for (pos = list_entry(pos->member.prev, typeof(*pos), member); \
- prefetch(pos->member.prev), &pos->member != (head); \
+ &pos->member != (head); \
pos = list_entry(pos->member.prev, typeof(*pos), member))
/**
@@ -483,7 +479,7 @@ static inline void list_splice_tail_init(struct list_head *list,
* Iterate over list of given type, continuing from current position.
*/
#define list_for_each_entry_from(pos, head, member) \
- for (; prefetch(pos->member.next), &pos->member != (head); \
+ for (; &pos->member != (head); \
pos = list_entry(pos->member.next, typeof(*pos), member))
/**
diff --git a/include/linux/rculist.h b/include/linux/rculist.h
index 900a97a44769..e3beb315517a 100644
--- a/include/linux/rculist.h
+++ b/include/linux/rculist.h
@@ -253,7 +253,7 @@ static inline void list_splice_init_rcu(struct list_head *list,
*/
#define list_for_each_entry_rcu(pos, head, member) \
for (pos = list_entry_rcu((head)->next, typeof(*pos), member); \
- prefetch(pos->member.next), &pos->member != (head); \
+ &pos->member != (head); \
pos = list_entry_rcu(pos->member.next, typeof(*pos), member))
@@ -270,7 +270,7 @@ static inline void list_splice_init_rcu(struct list_head *list,
*/
#define list_for_each_continue_rcu(pos, head) \
for ((pos) = rcu_dereference_raw(list_next_rcu(pos)); \
- prefetch((pos)->next), (pos) != (head); \
+ (pos) != (head); \
(pos) = rcu_dereference_raw(list_next_rcu(pos)))
/**
@@ -284,7 +284,7 @@ static inline void list_splice_init_rcu(struct list_head *list,
*/
#define list_for_each_entry_continue_rcu(pos, head, member) \
for (pos = list_entry_rcu(pos->member.next, typeof(*pos), member); \
- prefetch(pos->member.next), &pos->member != (head); \
+ &pos->member != (head); \
pos = list_entry_rcu(pos->member.next, typeof(*pos), member))
/**