[Qemu-devel] [PATCH 3/3] Samples to add a tracepoint.

[Prerna Saxena <prerna@linux.vnet.ibm.com>]

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Steps for adding a tracepoint :
1. In trace-entries.h, add a DECLARE_TRACE() in the said format.
2. In trace-entries.c:
     i) add a DEFINE_TRACE() for the tracepoint in the said format.
     ii) add an INIT_TRACE(name) for the tracepoint in the function 
init_tracepoints(void)
3. The call site should have a 'trace_name(args..)'
(Remember to include "trace-entries.h" in the file where the tracepoint 
is logged)

This patch adds tracepoints to virtio_blk_rw_complete() and paio_submit()

-- 
Prerna Saxena

Linux Technology Centre,
IBM Systems and Technology Lab,
Bangalore, India

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Signed-off by : Prerna (prerna@linux.vnet.ibm.com)

Index: qemu/hw/virtio-blk.c
===================================================================
--- qemu.orig/hw/virtio-blk.c
+++ qemu/hw/virtio-blk.c
@@ -19,6 +19,10 @@
 # include <scsi/sg.h>
 #endif
 
+#ifdef CONFIG_QEMU_TRACE
+#include "trace-entries.h"
+#endif
+
 typedef struct VirtIOBlock
 {
     VirtIODevice vdev;
@@ -87,6 +91,8 @@ static void virtio_blk_rw_complete(void 
 {
     VirtIOBlockReq *req = opaque;
 
+    trace_virtio_blk_rw_complete(req, ret);
+
     if (ret) {
         int is_read = !(req->out->type & VIRTIO_BLK_T_OUT);
         if (virtio_blk_handle_rw_error(req, -ret, is_read))
Index: qemu/posix-aio-compat.c
===================================================================
--- qemu.orig/posix-aio-compat.c
+++ qemu/posix-aio-compat.c
@@ -29,6 +29,9 @@
 
 #include "block/raw-posix-aio.h"
 
+#ifdef CONFIG_QEMU_TRACE
+#include "trace-entries.h"
+#endif
 
 struct qemu_paiocb {
     BlockDriverAIOCB common;
@@ -565,6 +568,7 @@ BlockDriverAIOCB *paio_submit(BlockDrive
 {
     struct qemu_paiocb *acb;
 
+    trace_paio_submit(fd, sector_num);
     acb = qemu_aio_get(&raw_aio_pool, bs, cb, opaque);
     if (!acb)
         return NULL;
Index: qemu/trace-entries.h
===================================================================
--- qemu.orig/trace-entries.h
+++ qemu/trace-entries.h
@@ -29,5 +29,20 @@ void init_tracepoints(void);
  * 		),
  * )
  */
+DECLARE_TRACE(virtio_blk_rw_complete,
+       TP_PROTO(void* req, int ret),
+       TP_STRUCT__entry(
+               __field(void*, req);
+               __field(int, ret);
+               )
+)
+
+DECLARE_TRACE(paio_submit,
+       TP_PROTO(int fd, int64_t sector_num),
+       TP_STRUCT__entry(
+               __field(int, fd);
+               __field(int64_t, sector_num);
+               )
+)
 
 #endif /*__TRACE_ENTRIES_H__ */
Index: qemu/trace-entries.c
===================================================================
--- qemu.orig/trace-entries.c
+++ qemu/trace-entries.c
@@ -20,7 +20,8 @@
 void init_tracepoints(void)
 {
 // INIT_TRACE(foo);
-
+   INIT_TRACE(virtio_blk_rw_complete);
+   INIT_TRACE(paio_submit);
    return;
 }
 
@@ -37,4 +38,23 @@ void init_tracepoints(void)
  * )
  *
  */
+DEFINE_TRACE( virtio_blk_rw_complete,
+       TP_PROTO(void* req, int ret),
+       TP_fast_assign(
+               __entry->req = req;
+               __entry->ret = ret;
+       ),
+       TP_printk("virtio_blk_rw_complete: req %p ret %d\n",__entry->req,
+		 __entry->ret)
+)
+
+DEFINE_TRACE( paio_submit,
+       TP_PROTO(int fd, int64_t sector_num),
+       TP_fast_assign(
+               __entry->fd = fd;
+               __entry->sector_num = sector_num;
+       ),
+       TP_printk("paio_submit: fd %d sector_num %ld\n",__entry->fd,
+						 __entry->sector_num)
+)