From 017d166066b6c8afe22b75f6dc5e91bfa8f9c67a Mon Sep 17 00:00:00 2001
From: Jens Axboe <axboe@suse.de>
Date: Mon, 6 Feb 2006 12:06:44 +0100
Subject: [PATCH] [PATCH] Allow trace data to stay CPU endianness

Basically just check whether we need to convert the trace or not
in blkparse, then we can get rid of the endianness conversion
in the hot path (blktrace:write_tip_events()).
---
 blkparse.c     | 28 ++++++++++++++++++++++++++--
 blkrawverify.c |  2 ++
 blktrace.c     |  2 --
 blktrace.h     | 43 +++++++++++++++++++++++++++----------------
 4 files changed, 55 insertions(+), 20 deletions(-)

diff --git a/blkparse.c b/blkparse.c
index 7da67a6..52078c4 100644
--- a/blkparse.c
+++ b/blkparse.c
@@ -245,6 +245,7 @@ static int ppi_hash_by_pid = 1;
 static int verbose;
 static unsigned int act_mask = -1U;
 static int stats_printed;
+static int data_is_native = -1;
 
 static unsigned int t_alloc_cache;
 static unsigned int bit_alloc_cache;
@@ -1773,6 +1774,22 @@ static int read_data(int fd, void *buffer, int bytes, int block, int *fdblock)
 	return 0;
 }
 
+static inline __u16 get_pdulen(struct blk_io_trace *bit)
+{
+	if (data_is_native)
+		return bit->pdu_len;
+
+	return __bswap_16(bit->pdu_len);
+}
+
+static inline __u32 get_magic(struct blk_io_trace *bit)
+{
+	if (data_is_native)
+		return bit->magic;
+
+	return __bswap_32(bit->magic);
+}
+
 static int read_events(int fd, int always_block, int *fdblock)
 {
 	struct per_dev_info *pdi = NULL;
@@ -1796,13 +1813,20 @@ static int read_events(int fd, int always_block, int *fdblock)
 			break;
 		}
 
-		magic = be32_to_cpu(bit->magic);
+		/*
+		 * look at first trace to check whether we need to convert
+		 * data in the future
+		 */
+		if (data_is_native == -1 && check_data_endianness(bit))
+			break;
+
+		magic = get_magic(bit);
 		if ((magic & 0xffffff00) != BLK_IO_TRACE_MAGIC) {
 			fprintf(stderr, "Bad magic %x\n", magic);
 			break;
 		}
 
-		pdu_len = be16_to_cpu(bit->pdu_len);
+		pdu_len = get_pdulen(bit);
 		if (pdu_len) {
 			void *ptr = realloc(bit, sizeof(*bit) + pdu_len);
 
diff --git a/blkrawverify.c b/blkrawverify.c
index 190f7ee..6cc9b29 100644
--- a/blkrawverify.c
+++ b/blkrawverify.c
@@ -33,6 +33,8 @@ struct trace_info {
 	char *string;
 };
 
+static int data_is_native = -1;
+
 #define TRACE_TO_STRING(f)	{.bit_field = f, .string = #f}
 static struct trace_info traces[] = {
 	TRACE_TO_STRING( BLK_TC_READ ),
diff --git a/blktrace.c b/blktrace.c
index 0054b87..a780481 100644
--- a/blktrace.c
+++ b/blktrace.c
@@ -494,8 +494,6 @@ static int flush_subbuf(struct thread_information *tip, struct tip_subbuf *ts)
 		if (offset + sizeof(*t) + pdu_len > ts->len)
 			break;
 
-		trace_to_be(t);
-
 		offset += sizeof(*t) + pdu_len;
 		tip->events_processed++;
 		events++;
diff --git a/blktrace.h b/blktrace.h
index af5ab66..13d6e03 100644
--- a/blktrace.h
+++ b/blktrace.h
@@ -53,6 +53,7 @@ struct per_cpu_info {
 };
 
 extern FILE *ofp;
+extern int data_is_native;
 
 #define CHECK_MAGIC(t)		(((t)->magic & 0xffffff00) == BLK_IO_TRACE_MAGIC)
 #define SUPPORTED_VERSION	(0x06)
@@ -90,24 +91,11 @@ static inline int verify_trace(struct blk_io_trace *t)
 	return 0;
 }
 
-static inline void trace_to_be(struct blk_io_trace *t)
-{
-	t->magic	= cpu_to_be32(t->magic);
-	t->sequence	= cpu_to_be32(t->sequence);
-	t->time		= cpu_to_be64(t->time);
-	t->sector	= cpu_to_be64(t->sector);
-	t->bytes	= cpu_to_be32(t->bytes);
-	t->action	= cpu_to_be32(t->action);
-	t->pid		= cpu_to_be32(t->pid);
-	t->cpu		= cpu_to_be32(t->cpu);
-	t->error	= cpu_to_be16(t->error);
-	t->pdu_len	= cpu_to_be16(t->pdu_len);
-	t->device	= cpu_to_be32(t->device);
-	/* t->comm is a string (endian neutral) */
-}
-
 static inline void trace_to_cpu(struct blk_io_trace *t)
 {
+	if (data_is_native)
+		return;
+
 	t->magic	= be32_to_cpu(t->magic);
 	t->sequence	= be32_to_cpu(t->sequence);
 	t->time		= be64_to_cpu(t->time);
@@ -122,6 +110,29 @@ static inline void trace_to_cpu(struct blk_io_trace *t)
 	/* t->comm is a string (endian neutral) */
 }
 
+/*
+ * check whether data is native or not
+ */
+static inline int check_data_endianness(struct blk_io_trace *bit)
+{
+	u32 magic;
+
+	if ((bit->magic & 0xffffff00) == BLK_IO_TRACE_MAGIC) {
+		fprintf(stderr, "data is native\n");
+		data_is_native = 1;
+		return 0;
+	}
+
+	magic = __bswap_32(bit->magic);
+	if ((magic & 0xffffff00) == BLK_IO_TRACE_MAGIC) {
+		fprintf(stderr, "data is not native\n");
+		data_is_native = 0;
+		return 0;
+	}
+
+	return 1;
+}
+
 extern void set_all_format_specs(char *);
 extern int add_format_spec(char *);
 extern void process_fmt(char *, struct per_cpu_info *, struct blk_io_trace *,
-- 
2.25.1