From 7c4a4849898e68581aecb2c197a87e9dd19da7d9 Mon Sep 17 00:00:00 2001
From: Thomas Preud'homme <thomas.preudhomme@celest.fr>
Date: Mon, 6 Jun 2011 13:34:01 +0200
Subject: [PATCH] [commtech] Simplify if's in send()

Test sender_ptr against the end of the current buffer via
channel->sender_ptr_end
---
 .../include/batch_queue_common_comm.h         | 55 ++++++-------------
 .../src/communication/batch_queue.c           |  8 ++-
 2 files changed, 25 insertions(+), 38 deletions(-)

diff --git a/communication_techniques/include/batch_queue_common_comm.h b/communication_techniques/include/batch_queue_common_comm.h
index 06c1884..ed640e8 100644
--- a/communication_techniques/include/batch_queue_common_comm.h
+++ b/communication_techniques/include/batch_queue_common_comm.h
@@ -15,64 +15,45 @@ struct channel
 {
 	/* buf must be the first field to allow the buf_mask test */
 	void * volatile buf[2][BUF_SIZE / sizeof(void *)] __attribute__ ((aligned (CACHE_LINE_SIZE)));
-	struct channel *mapping1; /* accesses to buf[0] and state */
-	struct channel *mapping2; /* accesses to buf[1] */
-	uintptr_t buf_mask;
 	int unused[20] __attribute__ ((aligned (CACHE_LINE_SIZE)));
 	volatile unsigned int  state:1 __attribute__ ((aligned (CACHE_LINE_SIZE)));
+
+	/* accesses to buf[0] and state */
+	struct channel *mapping1 __attribute__ ((aligned (CACHE_LINE_SIZE)));
+	/* accesses to buf[1] */
+	struct channel *mapping2;
+	void * volatile *buf_end1;
+	void * volatile *buf_end2;
+
 	void * volatile *sender_ptr __attribute__ ((aligned (CACHE_LINE_SIZE)));
+	void * volatile *sender_ptr_end;
 	void * volatile *receiver_ptr __attribute__ ((aligned (CACHE_LINE_SIZE)));
 };
 
-#ifndef _BATCH_QUEUE_C_
-#ifndef PAGE_SIZE_HELPER
-#define PAGE_SIZE_HELPER 1
-uintptr_t _bq_page_mask;
-void *create_comm_channel_internal(void);
-static void *create_comm_channel_helper(void) __attribute__ ((unused));
-
-static void *create_comm_channel_helper(void)
-{
-	int ret;
-	struct channel *channel;
-
-	ret = sysconf(_SC_PAGESIZE);
-	if (ret == -1)
-		return NULL;
-	_bq_page_mask = ~(ret - 1);
-	channel = create_comm_channel_internal();
-	channel->buf_mask = sizeof channel->buf[0] - 1;
-	return channel;
-}
-
-#else
-extern unsigned int _bq_page_mask;
-#endif /* PAGE_SIZE_HELPER */
-
-#define create_comm_channel() create_comm_channel_helper()
 
 __BEGIN_DECLS
 
 static inline void send(struct channel *channel, void **addr)
 {
-	uintptr_t sender_ptr_high;
 
 	*channel->sender_ptr++ = addr;
-	if (unlikely(!((uintptr_t) channel->sender_ptr & channel->buf_mask)))
+	if (unlikely(channel->sender_ptr == channel->sender_ptr_end))
 	{
 		while (channel->state);
 		channel->state = 1;
-		sender_ptr_high =
-			(uintptr_t) channel->sender_ptr & _bq_page_mask;
-		if ((void *) sender_ptr_high == channel->mapping1)
+		if (channel->sender_ptr_end == channel->buf_end1)
+		{
 			channel->sender_ptr = channel->mapping2->buf[1];
+			channel->sender_ptr_end = channel->buf_end2;
+		}
 		else
-			channel->sender_ptr = channel->mapping1->buf[0];
+		{
+			channel->sender_ptr = channel->buf[0];
+			channel->sender_ptr_end = channel->buf_end1;
+		}
 	}
 }
 
 __END_DECLS
 
-#endif /* _BATCH_QUEUE_C_ */
-
 #endif
diff --git a/communication_techniques/src/communication/batch_queue.c b/communication_techniques/src/communication/batch_queue.c
index 2bfb59a..9538800 100644
--- a/communication_techniques/src/communication/batch_queue.c
+++ b/communication_techniques/src/communication/batch_queue.c
@@ -23,7 +23,7 @@ static int nb_buf_entries;
 static unsigned int page_size;
 
 
-void *create_comm_channel_internal(void)
+void *create_comm_channel(void)
 {
 	int ret, shm_fd;
 	static int chan_idx = 0;
@@ -83,6 +83,12 @@ void *create_comm_channel_internal(void)
 	channel1->sender_ptr = channel1->buf[0];
 	channel1->receiver_ptr = channel1->buf[0];
 
+	channel1->buf_end1 = channel1->buf[0] +
+		(sizeof channel1->buf[0] / sizeof channel1->buf[0][0]);
+	channel1->buf_end2 = channel1->mapping2->buf[1] +
+		(sizeof channel1->buf[1] / sizeof channel1->buf[1][0]);
+	channel1->sender_ptr_end = channel1->buf_end1;
+
 	buf_mask = sizeof channel1->buf[0] - 1;
 	nb_buf_entries = sizeof channel1->buf[0] / sizeof channel1->buf[0][0];
 close_file: