[tip:core/futexes] plist: Shrink struct plist_head

From: tip-bot for Lai Jiangshan
Date: Sat Mar 12 2011 - 05:58:58 EST

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Commit-ID: bf6a9b8336ba12672755c2ae898b0abe42c7a5ac
Gitweb: http://git.kernel.org/tip/bf6a9b8336ba12672755c2ae898b0abe42c7a5ac
Author: Lai Jiangshan <laijs@xxxxxxxxxxxxxx>
AuthorDate: Tue, 21 Dec 2010 17:55:14 +0800
Committer: Steven Rostedt <rostedt@xxxxxxxxxxx>
CommitDate: Fri, 11 Mar 2011 15:13:26 -0500

plist: Shrink struct plist_head

struct plist_head is used in struct task_struct as well as struct
rtmutex. If we can make it smaller, it will also make these structures
smaller as well.

The field prio_list in struct plist_head is seldom used and we can get
its information from the plist_nodes. Removing this field will decrease
the size of plist_head by half.

Signed-off-by: Lai Jiangshan <laijs@xxxxxxxxxxxxxx>
LKML-Reference: <4D107982.9090700@xxxxxxxxxxxxxx>
Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
---
include/linux/plist.h | 47 +++++++++++++++++++++--------------------
lib/plist.c | 54 +++++++++++++++++++++++++++++++-----------------
2 files changed, 59 insertions(+), 42 deletions(-)

diff --git a/include/linux/plist.h b/include/linux/plist.h
index 7254eda..c9b9f32 100644
--- a/include/linux/plist.h
+++ b/include/linux/plist.h
@@ -31,15 +31,17 @@
*
* Simple ASCII art explanation:
*
- * |HEAD |
- * | |
- * |prio_list.prev|<------------------------------------|
- * |prio_list.next|<->|pl|<->|pl|<--------------->|pl|<-|
- * |10 | |10| |21| |21| |21| |40| (prio)
- * | | | | | | | | | | | |
- * | | | | | | | | | | | |
- * |node_list.next|<->|nl|<->|nl|<->|nl|<->|nl|<->|nl|<-|
- * |node_list.prev|<------------------------------------|
+ * pl:prio_list (only for plist_node)
+ * nl:node_list
+ * HEAD| NODE(S)
+ * |
+ * ||------------------------------------|
+ * ||->|pl|<->|pl|<--------------->|pl|<-|
+ * | |10| |21| |21| |21| |40| (prio)
+ * | | | | | | | | | | |
+ * | | | | | | | | | | |
+ * |->|nl|<->|nl|<->|nl|<->|nl|<->|nl|<->|nl|<-|
+ * |-------------------------------------------|
*
* The nodes on the prio_list list are sorted by priority to simplify
* the insertion of new nodes. There are no nodes with duplicate
@@ -78,7 +80,6 @@
#include <linux/spinlock_types.h>

struct plist_head {
- struct list_head prio_list;
struct list_head node_list;
#ifdef CONFIG_DEBUG_PI_LIST
raw_spinlock_t *rawlock;
@@ -88,7 +89,8 @@ struct plist_head {

struct plist_node {
int prio;
- struct plist_head plist;
+ struct list_head prio_list;
+ struct list_head node_list;
};

#ifdef CONFIG_DEBUG_PI_LIST
@@ -100,7 +102,6 @@ struct plist_node {
#endif

#define _PLIST_HEAD_INIT(head) \
- .prio_list = LIST_HEAD_INIT((head).prio_list), \
.node_list = LIST_HEAD_INIT((head).node_list)

/**
@@ -133,7 +134,8 @@ struct plist_node {
#define PLIST_NODE_INIT(node, __prio) \
{ \
.prio = (__prio), \
- .plist = { _PLIST_HEAD_INIT((node).plist) }, \
+ .prio_list = LIST_HEAD_INIT((node).prio_list), \
+ .node_list = LIST_HEAD_INIT((node).node_list), \
}

/**
@@ -144,7 +146,6 @@ struct plist_node {
static inline void
plist_head_init(struct plist_head *head, spinlock_t *lock)
{
- INIT_LIST_HEAD(&head->prio_list);
INIT_LIST_HEAD(&head->node_list);
#ifdef CONFIG_DEBUG_PI_LIST
head->spinlock = lock;
@@ -160,7 +161,6 @@ plist_head_init(struct plist_head *head, spinlock_t *lock)
static inline void
plist_head_init_raw(struct plist_head *head, raw_spinlock_t *lock)
{
- INIT_LIST_HEAD(&head->prio_list);
INIT_LIST_HEAD(&head->node_list);
#ifdef CONFIG_DEBUG_PI_LIST
head->rawlock = lock;
@@ -176,7 +176,8 @@ plist_head_init_raw(struct plist_head *head, raw_spinlock_t *lock)
static inline void plist_node_init(struct plist_node *node, int prio)
{
node->prio = prio;
- plist_head_init(&node->plist, NULL);
+ INIT_LIST_HEAD(&node->prio_list);
+ INIT_LIST_HEAD(&node->node_list);
}

extern void plist_add(struct plist_node *node, struct plist_head *head);
@@ -188,7 +189,7 @@ extern void plist_del(struct plist_node *node, struct plist_head *head);
* @head: the head for your list
*/
#define plist_for_each(pos, head) \
- list_for_each_entry(pos, &(head)->node_list, plist.node_list)
+ list_for_each_entry(pos, &(head)->node_list, node_list)

/**
* plist_for_each_safe - iterate safely over a plist of given type
@@ -199,7 +200,7 @@ extern void plist_del(struct plist_node *node, struct plist_head *head);
* Iterate over a plist of given type, safe against removal of list entry.
*/
#define plist_for_each_safe(pos, n, head) \
- list_for_each_entry_safe(pos, n, &(head)->node_list, plist.node_list)
+ list_for_each_entry_safe(pos, n, &(head)->node_list, node_list)

/**
* plist_for_each_entry - iterate over list of given type
@@ -208,7 +209,7 @@ extern void plist_del(struct plist_node *node, struct plist_head *head);
* @mem: the name of the list_struct within the struct
*/
#define plist_for_each_entry(pos, head, mem) \
- list_for_each_entry(pos, &(head)->node_list, mem.plist.node_list)
+ list_for_each_entry(pos, &(head)->node_list, mem.node_list)

/**
* plist_for_each_entry_safe - iterate safely over list of given type
@@ -220,7 +221,7 @@ extern void plist_del(struct plist_node *node, struct plist_head *head);
* Iterate over list of given type, safe against removal of list entry.
*/
#define plist_for_each_entry_safe(pos, n, head, m) \
- list_for_each_entry_safe(pos, n, &(head)->node_list, m.plist.node_list)
+ list_for_each_entry_safe(pos, n, &(head)->node_list, m.node_list)

/**
* plist_head_empty - return !0 if a plist_head is empty
@@ -237,7 +238,7 @@ static inline int plist_head_empty(const struct plist_head *head)
*/
static inline int plist_node_empty(const struct plist_node *node)
{
- return plist_head_empty(&node->plist);
+ return list_empty(&node->node_list);
}

/* All functions below assume the plist_head is not empty. */
@@ -285,7 +286,7 @@ static inline int plist_node_empty(const struct plist_node *node)
static inline struct plist_node *plist_first(const struct plist_head *head)
{
return list_entry(head->node_list.next,
- struct plist_node, plist.node_list);
+ struct plist_node, node_list);
}

/**
@@ -297,7 +298,7 @@ static inline struct plist_node *plist_first(const struct plist_head *head)
static inline struct plist_node *plist_last(const struct plist_head *head)
{
return list_entry(head->node_list.prev,
- struct plist_node, plist.node_list);
+ struct plist_node, node_list);
}

#endif
diff --git a/lib/plist.c b/lib/plist.c
index 1471988..8c614d0 100644
--- a/lib/plist.c
+++ b/lib/plist.c
@@ -59,7 +59,8 @@ static void plist_check_head(struct plist_head *head)
WARN_ON_SMP(!raw_spin_is_locked(head->rawlock));
if (head->spinlock)
WARN_ON_SMP(!spin_is_locked(head->spinlock));
- plist_check_list(&head->prio_list);
+ if (!plist_head_empty(head))
+ plist_check_list(&plist_first(head)->prio_list);
plist_check_list(&head->node_list);
}

@@ -75,25 +76,33 @@ static void plist_check_head(struct plist_head *head)
*/
void plist_add(struct plist_node *node, struct plist_head *head)
{
- struct plist_node *iter;
+ struct plist_node *first, *iter, *prev = NULL;
+ struct list_head *node_next = &head->node_list;

plist_check_head(head);
WARN_ON(!plist_node_empty(node));
+ WARN_ON(!list_empty(&node->prio_list));

- list_for_each_entry(iter, &head->prio_list, plist.prio_list) {
- if (node->prio < iter->prio)
- goto lt_prio;
- else if (node->prio == iter->prio) {
- iter = list_entry(iter->plist.prio_list.next,
- struct plist_node, plist.prio_list);
- goto eq_prio;
+ if (plist_head_empty(head))
+ goto ins_node;
+
+ first = iter = plist_first(head);
+
+ do {
+ if (node->prio < iter->prio) {
+ node_next = &iter->node_list;
+ break;
}
- }

-lt_prio:
- list_add_tail(&node->plist.prio_list, &iter->plist.prio_list);
-eq_prio:
- list_add_tail(&node->plist.node_list, &iter->plist.node_list);
+ prev = iter;
+ iter = list_entry(iter->prio_list.next,
+ struct plist_node, prio_list);
+ } while (iter != first);
+
+ if (!prev || prev->prio != node->prio)
+ list_add_tail(&node->prio_list, &iter->prio_list);
+ins_node:
+ list_add_tail(&node->node_list, node_next);

plist_check_head(head);
}
@@ -108,14 +117,21 @@ void plist_del(struct plist_node *node, struct plist_head *head)
{
plist_check_head(head);

- if (!list_empty(&node->plist.prio_list)) {
- struct plist_node *next = plist_first(&node->plist);
+ if (!list_empty(&node->prio_list)) {
+ if (node->node_list.next != &head->node_list) {
+ struct plist_node *next;
+
+ next = list_entry(node->node_list.next,
+ struct plist_node, node_list);

- list_move_tail(&next->plist.prio_list, &node->plist.prio_list);
- list_del_init(&node->plist.prio_list);
+ /* add the next plist_node into prio_list */
+ if (list_empty(&next->prio_list))
+ list_add(&next->prio_list, &node->prio_list);
+ }
+ list_del_init(&node->prio_list);
}

- list_del_init(&node->plist.node_list);
+ list_del_init(&node->node_list);

plist_check_head(head);
}
--
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Next message: tip-bot for Lai Jiangshan: "[tip:core/futexes] plist: Add priority list test"
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