0120-do-accept-in-LIFO-order-for-cache-efficiency.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Arjan van de Ven <arjan@linux.intel.com>
Date: Thu, 13 Dec 2018 01:00:49 +0000
Subject: [PATCH] do accept() in LIFO order for cache efficiency

---
 include/linux/wait.h            |  2 ++
 kernel/sched/wait.c             | 24 ++++++++++++++++++++++++
 net/ipv4/inet_connection_sock.c |  2 +-
 3 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/include/linux/wait.h b/include/linux/wait.h
index 851e07da2583..85653fc33274 100644
--- a/include/linux/wait.h
+++ b/include/linux/wait.h
@@ -165,6 +165,7 @@ static inline bool wq_has_sleeper(struct wait_queue_head *wq_head)
 
 extern void add_wait_queue(struct wait_queue_head *wq_head, struct wait_queue_entry *wq_entry);
 extern void add_wait_queue_exclusive(struct wait_queue_head *wq_head, struct wait_queue_entry *wq_entry);
+extern void add_wait_queue_exclusive_lifo(struct wait_queue_head *wq_head, struct wait_queue_entry *wq_entry);
 extern void add_wait_queue_priority(struct wait_queue_head *wq_head, struct wait_queue_entry *wq_entry);
 extern void remove_wait_queue(struct wait_queue_head *wq_head, struct wait_queue_entry *wq_entry);
 
@@ -1163,6 +1164,7 @@ do {										\
  */
 void prepare_to_wait(struct wait_queue_head *wq_head, struct wait_queue_entry *wq_entry, int state);
 bool prepare_to_wait_exclusive(struct wait_queue_head *wq_head, struct wait_queue_entry *wq_entry, int state);
+void prepare_to_wait_exclusive_lifo(struct wait_queue_head *wq_head, struct wait_queue_entry *wq_entry, int state);
 long prepare_to_wait_event(struct wait_queue_head *wq_head, struct wait_queue_entry *wq_entry, int state);
 void finish_wait(struct wait_queue_head *wq_head, struct wait_queue_entry *wq_entry);
 long wait_woken(struct wait_queue_entry *wq_entry, unsigned mode, long timeout);
diff --git a/kernel/sched/wait.c b/kernel/sched/wait.c
index eca38107b32f..0306fa23b4f8 100644
--- a/kernel/sched/wait.c
+++ b/kernel/sched/wait.c
@@ -48,6 +48,17 @@ void add_wait_queue_priority(struct wait_queue_head *wq_head, struct wait_queue_
 }
 EXPORT_SYMBOL_GPL(add_wait_queue_priority);
 
+void add_wait_queue_exclusive_lifo(struct wait_queue_head *wq_head, struct wait_queue_entry *wq_entry)
+{
+	unsigned long flags;
+
+	wq_entry->flags |= WQ_FLAG_EXCLUSIVE;
+	spin_lock_irqsave(&wq_head->lock, flags);
+	__add_wait_queue(wq_head, wq_entry);
+	spin_unlock_irqrestore(&wq_head->lock, flags);
+}
+EXPORT_SYMBOL(add_wait_queue_exclusive_lifo);
+
 void remove_wait_queue(struct wait_queue_head *wq_head, struct wait_queue_entry *wq_entry)
 {
 	unsigned long flags;
@@ -290,6 +301,19 @@ prepare_to_wait_exclusive(struct wait_queue_head *wq_head, struct wait_queue_ent
 }
 EXPORT_SYMBOL(prepare_to_wait_exclusive);
 
+void prepare_to_wait_exclusive_lifo(struct wait_queue_head *wq_head, struct wait_queue_entry *wq_entry, int state)
+{
+	unsigned long flags;
+
+	wq_entry->flags |= WQ_FLAG_EXCLUSIVE;
+	spin_lock_irqsave(&wq_head->lock, flags);
+	if (list_empty(&wq_entry->entry))
+		__add_wait_queue(wq_head, wq_entry);
+	set_current_state(state);
+	spin_unlock_irqrestore(&wq_head->lock, flags);
+}
+EXPORT_SYMBOL(prepare_to_wait_exclusive_lifo);
+
 void init_wait_entry(struct wait_queue_entry *wq_entry, int flags)
 {
 	wq_entry->flags = flags;
diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
index fc2a985f6064..02dc861de3d5 100644
--- a/net/ipv4/inet_connection_sock.c
+++ b/net/ipv4/inet_connection_sock.c
@@ -441,7 +441,7 @@ static int inet_csk_wait_for_connect(struct sock *sk, long timeo)
 	 * having to remove and re-insert us on the wait queue.
 	 */
 	for (;;) {
-		prepare_to_wait_exclusive(sk_sleep(sk), &wait,
+		prepare_to_wait_exclusive_lifo(sk_sleep(sk), &wait,
 					  TASK_INTERRUPTIBLE);
 		release_sock(sk);
 		if (reqsk_queue_empty(&icsk->icsk_accept_queue))
-- 
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