tracing/events: convert block trace points to TRACE_EVENT()

TRACE_EVENT is a more generic way to define tracepoints. Doing so adds
these new capabilities to this tracepoint:

  - zero-copy and per-cpu splice() tracing
  - binary tracing without printf overhead
  - structured logging records exposed under /debug/tracing/events
  - trace events embedded in function tracer output and other plugins
  - user-defined, per tracepoint filter expressions
  ...

Cons:

  - no dev_t info for the output of plug, unplug_timer and unplug_io events.
    no dev_t info for getrq and sleeprq events if bio == NULL.
    no dev_t info for rq_abort,...,rq_requeue events if rq->rq_disk == NULL.

    This is mainly because we can't get the deivce from a request queue.
    But this may change in the future.

  - A packet command is converted to a string in TP_assign, not TP_print.
    While blktrace do the convertion just before output.

    Since pc requests should be rather rare, this is not a big issue.

  - In blktrace, an event can have 2 different print formats, but a TRACE_EVENT
    has a unique format, which means we have some unused data in a trace entry.

    The overhead is minimized by using __dynamic_array() instead of __array().

I've benchmarked the ioctl blktrace vs the splice based TRACE_EVENT tracing:

      dd                   dd + ioctl blktrace       dd + TRACE_EVENT (splice)
1     7.36s, 42.7 MB/s     7.50s, 42.0 MB/s          7.41s, 42.5 MB/s
2     7.43s, 42.3 MB/s     7.48s, 42.1 MB/s          7.43s, 42.4 MB/s
3     7.38s, 42.6 MB/s     7.45s, 42.2 MB/s          7.41s, 42.5 MB/s

So the overhead of tracing is very small, and no regression when using
those trace events vs blktrace.

And the binary output of TRACE_EVENT is much smaller than blktrace:

 # ls -l -h
 -rw-r--r-- 1 root root 8.8M 06-09 13:24 sda.blktrace.0
 -rw-r--r-- 1 root root 195K 06-09 13:24 sda.blktrace.1
 -rw-r--r-- 1 root root 2.7M 06-09 13:25 trace_splice.out

Following are some comparisons between TRACE_EVENT and blktrace:

plug:
  kjournald-480   [000]   303.084981: block_plug: [kjournald]
  kjournald-480   [000]   303.084981:   8,0    P   N [kjournald]

unplug_io:
  kblockd/0-118   [000]   300.052973: block_unplug_io: [kblockd/0] 1
  kblockd/0-118   [000]   300.052974:   8,0    U   N [kblockd/0] 1

remap:
  kjournald-480   [000]   303.085042: block_remap: 8,0 W 102736992 + 8 <- (8,8) 33384
  kjournald-480   [000]   303.085043:   8,0    A   W 102736992 + 8 <- (8,8) 33384

bio_backmerge:
  kjournald-480   [000]   303.085086: block_bio_backmerge: 8,0 W 102737032 + 8 [kjournald]
  kjournald-480   [000]   303.085086:   8,0    M   W 102737032 + 8 [kjournald]

getrq:
  kjournald-480   [000]   303.084974: block_getrq: 8,0 W 102736984 + 8 [kjournald]
  kjournald-480   [000]   303.084975:   8,0    G   W 102736984 + 8 [kjournald]

  bash-2066  [001]  1072.953770:   8,0    G   N [bash]
  bash-2066  [001]  1072.953773: block_getrq: 0,0 N 0 + 0 [bash]

rq_complete:
  konsole-2065  [001]   300.053184: block_rq_complete: 8,0 W () 103669040 + 16 [0]
  konsole-2065  [001]   300.053191:   8,0    C   W 103669040 + 16 [0]

  ksoftirqd/1-7   [001]  1072.953811:   8,0    C   N (5a 00 08 00 00 00 00 00 24 00) [0]
  ksoftirqd/1-7   [001]  1072.953813: block_rq_complete: 0,0 N (5a 00 08 00 00 00 00 00 24 00) 0 + 0 [0]

rq_insert:
  kjournald-480   [000]   303.084985: block_rq_insert: 8,0 W 0 () 102736984 + 8 [kjournald]
  kjournald-480   [000]   303.084986:   8,0    I   W 102736984 + 8 [kjournald]

Changelog from v2 -> v3:

- use the newly introduced __dynamic_array().

Changelog from v1 -> v2:

- use __string() instead of __array() to minimize the memory required
  to store hex dump of rq->cmd().

- support large pc requests.

- add missing blk_fill_rwbs_rq() in block_rq_requeue TRACE_EVENT.

- some cleanups.
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
LKML-Reference: <4A2DF669.5070905@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

block/blk-core.c

@@ -28,22 +28,14 @@
 #include <linux/task_io_accounting_ops.h>
 #include <linux/blktrace_api.h>
 #include <linux/fault-inject.h>
-#include <trace/block.h>
+
+#define CREATE_TRACE_POINTS
+#include <trace/events/block.h>
 
 #include "blk.h"
 
-DEFINE_TRACE(block_plug);
-DEFINE_TRACE(block_unplug_io);
-DEFINE_TRACE(block_unplug_timer);
-DEFINE_TRACE(block_getrq);
-DEFINE_TRACE(block_sleeprq);
-DEFINE_TRACE(block_rq_requeue);
-DEFINE_TRACE(block_bio_backmerge);
-DEFINE_TRACE(block_bio_frontmerge);
-DEFINE_TRACE(block_bio_queue);
-DEFINE_TRACE(block_rq_complete);
-DEFINE_TRACE(block_remap);	/* Also used in drivers/md/dm.c */
 EXPORT_TRACEPOINT_SYMBOL_GPL(block_remap);
+EXPORT_TRACEPOINT_SYMBOL_GPL(block_bio_complete);
 
 static int __make_request(struct request_queue *q, struct bio *bio);
 

block/elevator.c

@@ -33,17 +33,16 @@
 #include <linux/compiler.h>
 #include <linux/delay.h>
 #include <linux/blktrace_api.h>
-#include <trace/block.h>
 #include <linux/hash.h>
 #include <linux/uaccess.h>
 
+#include <trace/events/block.h>
+
 #include "blk.h"
 
 static DEFINE_SPINLOCK(elv_list_lock);
 static LIST_HEAD(elv_list);
 
-DEFINE_TRACE(block_rq_abort);
-
 /*
  * Merge hash stuff.
  */
@@ -55,9 +54,6 @@ static const int elv_hash_shift = 6;
 #define rq_hash_key(rq)		((rq)->sector + (rq)->nr_sectors)
 #define ELV_ON_HASH(rq)		(!hlist_unhashed(&(rq)->hash))
 
-DEFINE_TRACE(block_rq_insert);
-DEFINE_TRACE(block_rq_issue);
-
 /*
  * Query io scheduler to see if the current process issuing bio may be
  * merged with rq.

drivers/md/dm.c

@@ -20,7 +20,8 @@
 #include <linux/idr.h>
 #include <linux/hdreg.h>
 #include <linux/blktrace_api.h>
-#include <trace/block.h>
+
+#include <trace/events/block.h>
 
 #define DM_MSG_PREFIX "core"
 
@@ -53,8 +54,6 @@ struct dm_target_io {
 	union map_info info;
 };
 
-DEFINE_TRACE(block_bio_complete);
-
 /*
  * For request-based dm.
  * One of these is allocated per request.

fs/bio.c

@@ -26,10 +26,9 @@
 #include <linux/mempool.h>
 #include <linux/workqueue.h>
 #include <linux/blktrace_api.h>
-#include <trace/block.h>
 #include <scsi/sg.h>		/* for struct sg_iovec */
 
-DEFINE_TRACE(block_split);
+#include <trace/events/block.h>
 
 /*
  * Test patch to inline a certain number of bi_io_vec's inside the bio

include/linux/blktrace_api.h

@@ -218,5 +218,18 @@ static inline int blk_trace_init_sysfs(struct device *dev)
 
 #endif /* CONFIG_BLK_DEV_IO_TRACE */
 
+#ifdef CONFIG_EVENT_TRACING
+
+static inline int blk_cmd_buf_len(struct request *rq)
+{
+	return blk_pc_request(rq) ? rq->cmd_len * 3 : 1;
+}
+
+extern void blk_dump_cmd(char *buf, struct request *rq);
+extern void blk_fill_rwbs(char *rwbs, u32 rw, int bytes);
+extern void blk_fill_rwbs_rq(char *rwbs, struct request *rq);
+
+#endif /* CONFIG_EVENT_TRACING */
+
 #endif /* __KERNEL__ */
 #endif

include/trace/block.h

-#ifndef _TRACE_BLOCK_H
-#define _TRACE_BLOCK_H
-
-#include <linux/blkdev.h>
-#include <linux/tracepoint.h>
-
-DECLARE_TRACE(block_rq_abort,
-	TP_PROTO(struct request_queue *q, struct request *rq),
-	      TP_ARGS(q, rq));
-
-DECLARE_TRACE(block_rq_insert,
-	TP_PROTO(struct request_queue *q, struct request *rq),
-	      TP_ARGS(q, rq));
-
-DECLARE_TRACE(block_rq_issue,
-	TP_PROTO(struct request_queue *q, struct request *rq),
-	      TP_ARGS(q, rq));
-
-DECLARE_TRACE(block_rq_requeue,
-	TP_PROTO(struct request_queue *q, struct request *rq),
-	      TP_ARGS(q, rq));
-
-DECLARE_TRACE(block_rq_complete,
-	TP_PROTO(struct request_queue *q, struct request *rq),
-	      TP_ARGS(q, rq));
-
-DECLARE_TRACE(block_bio_bounce,
-	TP_PROTO(struct request_queue *q, struct bio *bio),
-	      TP_ARGS(q, bio));
-
-DECLARE_TRACE(block_bio_complete,
-	TP_PROTO(struct request_queue *q, struct bio *bio),
-	      TP_ARGS(q, bio));
-
-DECLARE_TRACE(block_bio_backmerge,
-	TP_PROTO(struct request_queue *q, struct bio *bio),
-	      TP_ARGS(q, bio));
-
-DECLARE_TRACE(block_bio_frontmerge,
-	TP_PROTO(struct request_queue *q, struct bio *bio),
-	      TP_ARGS(q, bio));
-
-DECLARE_TRACE(block_bio_queue,
-	TP_PROTO(struct request_queue *q, struct bio *bio),
-	      TP_ARGS(q, bio));
-
-DECLARE_TRACE(block_getrq,
-	TP_PROTO(struct request_queue *q, struct bio *bio, int rw),
-	      TP_ARGS(q, bio, rw));
-
-DECLARE_TRACE(block_sleeprq,
-	TP_PROTO(struct request_queue *q, struct bio *bio, int rw),
-	      TP_ARGS(q, bio, rw));
-
-DECLARE_TRACE(block_plug,
-	TP_PROTO(struct request_queue *q),
-	      TP_ARGS(q));
-
-DECLARE_TRACE(block_unplug_timer,
-	TP_PROTO(struct request_queue *q),
-	      TP_ARGS(q));
-
-DECLARE_TRACE(block_unplug_io,
-	TP_PROTO(struct request_queue *q),
-	      TP_ARGS(q));
-
-DECLARE_TRACE(block_split,
-	TP_PROTO(struct request_queue *q, struct bio *bio, unsigned int pdu),
-	      TP_ARGS(q, bio, pdu));
-
-DECLARE_TRACE(block_remap,
-	TP_PROTO(struct request_queue *q, struct bio *bio, dev_t dev,
-		 sector_t from),
-	      TP_ARGS(q, bio, dev, from));
-
-#endif

kernel/trace/Makefile

@@ -46,6 +46,9 @@ obj-$(CONFIG_POWER_TRACER) += trace_power.o
 obj-$(CONFIG_KMEMTRACE) += kmemtrace.o
 obj-$(CONFIG_WORKQUEUE_TRACER) += trace_workqueue.o
 obj-$(CONFIG_BLK_DEV_IO_TRACE) += blktrace.o
+ifeq ($(CONFIG_BLOCK),y)
+obj-$(CONFIG_EVENT_TRACING) += blktrace.o
+endif
 obj-$(CONFIG_EVENT_TRACING) += trace_events.o
 obj-$(CONFIG_EVENT_TRACING) += trace_export.o
 obj-$(CONFIG_FTRACE_SYSCALLS) += trace_syscalls.o

kernel/trace/blktrace.c

@@ -23,10 +23,14 @@
 #include <linux/mutex.h>
 #include <linux/debugfs.h>
 #include <linux/time.h>
-#include <trace/block.h>
 #include <linux/uaccess.h>
+
+#include <trace/events/block.h>
+
 #include "trace_output.h"
 
+#ifdef CONFIG_BLK_DEV_IO_TRACE
+
 static unsigned int blktrace_seq __read_mostly = 1;
 
 static struct trace_array *blk_tr;
@@ -1658,3 +1662,75 @@ int blk_trace_init_sysfs(struct device *dev)
 	return sysfs_create_group(&dev->kobj, &blk_trace_attr_group);
 }
 
+#endif /* CONFIG_BLK_DEV_IO_TRACE */
+
+#ifdef CONFIG_EVENT_TRACING
+
+void blk_dump_cmd(char *buf, struct request *rq)
+{
+	int i, end;
+	int len = rq->cmd_len;
+	unsigned char *cmd = rq->cmd;
+
+	if (!blk_pc_request(rq)) {
+		buf[0] = '\0';
+		return;
+	}
+
+	for (end = len - 1; end >= 0; end--)
+		if (cmd[end])
+			break;
+	end++;
+
+	for (i = 0; i < len; i++) {
+		buf += sprintf(buf, "%s%02x", i == 0 ? "" : " ", cmd[i]);
+		if (i == end && end != len - 1) {
+			sprintf(buf, " ..");
+			break;
+		}
+	}
+}
+
+void blk_fill_rwbs(char *rwbs, u32 rw, int bytes)
+{
+	int i = 0;
+
+	if (rw & WRITE)
+		rwbs[i++] = 'W';
+	else if (rw & 1 << BIO_RW_DISCARD)
+		rwbs[i++] = 'D';
+	else if (bytes)
+		rwbs[i++] = 'R';
+	else
+		rwbs[i++] = 'N';
+
+	if (rw & 1 << BIO_RW_AHEAD)
+		rwbs[i++] = 'A';
+	if (rw & 1 << BIO_RW_BARRIER)
+		rwbs[i++] = 'B';
+	if (rw & 1 << BIO_RW_SYNCIO)
+		rwbs[i++] = 'S';
+	if (rw & 1 << BIO_RW_META)
+		rwbs[i++] = 'M';
+
+	rwbs[i] = '\0';
+}
+
+void blk_fill_rwbs_rq(char *rwbs, struct request *rq)
+{
+	int rw = rq->cmd_flags & 0x03;
+	int bytes;
+
+	if (blk_discard_rq(rq))
+		rw |= (1 << BIO_RW_DISCARD);
+
+	if (blk_pc_request(rq))
+		bytes = rq->data_len;
+	else
+		bytes = rq->hard_nr_sectors << 9;
+
+	blk_fill_rwbs(rwbs, rw, bytes);
+}
+
+#endif /* CONFIG_EVENT_TRACING */
+

mm/bounce.c

@@ -14,16 +14,15 @@
 #include <linux/hash.h>
 #include <linux/highmem.h>
 #include <linux/blktrace_api.h>
-#include <trace/block.h>
 #include <asm/tlbflush.h>
 
+#include <trace/events/block.h>
+
 #define POOL_SIZE	64
 #define ISA_POOL_SIZE	16
 
 static mempool_t *page_pool, *isa_page_pool;
 
-DEFINE_TRACE(block_bio_bounce);
-
 #ifdef CONFIG_HIGHMEM
 static __init int init_emergency_pool(void)
 {