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Message-ID: <20130321114313.GA17275@dcvr.yhbt.net>
Date: Thu, 21 Mar 2013 11:43:13 +0000
From: Eric Wong <normalperson@...t.net>
To: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc: Lai Jiangshan <laijs@...fujitsu.com>,
"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
Stephen Hemminger <shemminger@...tta.com>,
Davide Libenzi <davidel@...ilserver.org>,
linux-kernel@...r.kernel.org
Subject: [PATCH] wfcqueue: functions for local append and enqueue
With level-triggered epoll, append/enqueue operations to the
local/locked queues increase performance by avoiding unnecessary atomic
operations and barriers. These are necessary to avoid performance
regressions when looping through ep_send_events and appending many
items to a queue.
Signed-off-by: Eric Wong <normalperson@...t.net>
Cc: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc: Lai Jiangshan <laijs@...fujitsu.com>
Cc: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
Cc: Stephen Hemminger <shemminger@...tta.com>
Cc: Davide Libenzi <davidel@...ilserver.org>
---
Benchmark for this coming with updated epoll patches.
include/linux/wfcqueue.h | 43 +++++++++++++++++++++++++++++++++++++++++++
1 file changed, 43 insertions(+)
diff --git a/include/linux/wfcqueue.h b/include/linux/wfcqueue.h
index 9464a0c..7eb2aaa 100644
--- a/include/linux/wfcqueue.h
+++ b/include/linux/wfcqueue.h
@@ -205,6 +205,49 @@ static inline bool wfcq_enqueue(struct wfcq_head *head,
}
/*
+ * __wfcq_append_local: append one local queue to another local queue
+ *
+ * No memory barriers are issued. Mutual exclusion is the responsibility
+ * of the caller.
+ *
+ * Returns false if the queue was empty prior to adding the node.
+ * Returns true otherwise.
+ */
+static inline bool __wfcq_append_local(struct wfcq_head *head,
+ struct wfcq_tail *tail,
+ struct wfcq_node *new_head,
+ struct wfcq_node *new_tail)
+{
+ struct wfcq_node *old_tail;
+
+ old_tail = tail->p;
+ tail->p = new_tail;
+ old_tail->next = new_head;
+
+ /*
+ * Return false if queue was empty prior to adding the node,
+ * else return true.
+ */
+ return old_tail != &head->node;
+}
+
+/*
+ * wfcq_enqueue_local: enqueue a node into a local wait-free queue
+ *
+ * No memory barriers are issued. Mutual exclusion is the responsibility
+ * of the caller.
+ *
+ * Returns false if the queue was empty prior to adding the node.
+ * Returns true otherwise.
+ */
+static inline bool wfcq_enqueue_local(struct wfcq_head *head,
+ struct wfcq_tail *tail,
+ struct wfcq_node *new_tail)
+{
+ return __wfcq_append_local(head, tail, new_tail, new_tail);
+}
+
+/*
* ___wfcq_busy_wait: busy-wait.
*/
static inline void ___wfcq_busy_wait(void)
--
1.8.2.rc3.2.g89ce8d6
--
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