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plist: Shrink struct plist_head
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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@cn.fujitsu.com>
LKML-Reference: <4D107982.9090700@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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Lai Jiangshan authored and Steven Rostedt committed Mar 11, 2011
1 parent 017f2b2 commit bf6a9b8
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Showing 2 changed files with 59 additions and 42 deletions.
47 changes: 24 additions & 23 deletions include/linux/plist.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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
Expand Down Expand Up @@ -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;
Expand All @@ -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
Expand All @@ -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)

/**
Expand Down Expand Up @@ -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), \
}

/**
Expand All @@ -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;
Expand All @@ -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;
Expand All @@ -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);
Expand All @@ -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
Expand All @@ -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
Expand All @@ -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
Expand All @@ -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
Expand All @@ -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. */
Expand Down Expand Up @@ -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);
}

/**
Expand All @@ -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
54 changes: 35 additions & 19 deletions lib/plist.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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);
}

Expand All @@ -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);
}
Expand All @@ -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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