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Subject[PATCH 15/18] writeback: trace event writeback_single_inode
It is valuable to know how the dirty inodes are iterated and their IO size.

"writeback_single_inode: bdi 8:0: ino=134246746 state=I_DIRTY_SYNC|I_SYNC age=414 index=0 to_write=1024 wrote=0"
- "state" reflects inode->i_state at the end of writeback_single_inode()
- "index" reflects mapping->writeback_index after the ->writepages() call
- "to_write" is the wbc->nr_to_write at entrance of writeback_single_inode()
- "wrote" is the number of pages actually written

v2: add trace event writeback_single_inode_requeue as proposed by Dave.

CC: Dave Chinner <david@fromorbit.com>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
---
fs/fs-writeback.c | 4 +
include/trace/events/writeback.h | 70 +++++++++++++++++++++++++++++
2 files changed, 74 insertions(+)
--- linux-next.orig/include/trace/events/writeback.h 2011-05-24 11:17:25.000000000 +0800
+++ linux-next/include/trace/events/writeback.h 2011-05-24 11:17:26.000000000 +0800
@@ -8,6 +8,19 @@
#include <linux/device.h>
#include <linux/writeback.h>

+#define show_inode_state(state) \
+ __print_flags(state, "|", \
+ {I_DIRTY_SYNC, "I_DIRTY_SYNC"}, \
+ {I_DIRTY_DATASYNC, "I_DIRTY_DATASYNC"}, \
+ {I_DIRTY_PAGES, "I_DIRTY_PAGES"}, \
+ {I_NEW, "I_NEW"}, \
+ {I_WILL_FREE, "I_WILL_FREE"}, \
+ {I_FREEING, "I_FREEING"}, \
+ {I_CLEAR, "I_CLEAR"}, \
+ {I_SYNC, "I_SYNC"}, \
+ {I_REFERENCED, "I_REFERENCED"} \
+ )
+
struct wb_writeback_work;

DECLARE_EVENT_CLASS(writeback_work_class,
@@ -184,6 +197,63 @@ DEFINE_EVENT(writeback_congest_waited_te
TP_ARGS(usec_timeout, usec_delayed)
);

+DECLARE_EVENT_CLASS(writeback_single_inode_template,
+
+ TP_PROTO(struct inode *inode,
+ struct writeback_control *wbc,
+ unsigned long nr_to_write
+ ),
+
+ TP_ARGS(inode, wbc, nr_to_write),
+
+ TP_STRUCT__entry(
+ __array(char, name, 32)
+ __field(unsigned long, ino)
+ __field(unsigned long, state)
+ __field(unsigned long, age)
+ __field(unsigned long, writeback_index)
+ __field(long, nr_to_write)
+ __field(unsigned long, wrote)
+ ),
+
+ TP_fast_assign(
+ strncpy(__entry->name,
+ dev_name(inode->i_mapping->backing_dev_info->dev), 32);
+ __entry->ino = inode->i_ino;
+ __entry->state = inode->i_state;
+ __entry->age = (jiffies - inode->dirtied_when) *
+ 1000 / HZ;
+ __entry->writeback_index = inode->i_mapping->writeback_index;
+ __entry->nr_to_write = nr_to_write;
+ __entry->wrote = nr_to_write - wbc->nr_to_write;
+ ),
+
+ TP_printk("bdi %s: ino=%lu state=%s age=%lu "
+ "index=%lu to_write=%ld wrote=%lu",
+ __entry->name,
+ __entry->ino,
+ show_inode_state(__entry->state),
+ __entry->age,
+ __entry->writeback_index,
+ __entry->nr_to_write,
+ __entry->wrote
+ )
+);
+
+DEFINE_EVENT(writeback_single_inode_template, writeback_single_inode_requeue,
+ TP_PROTO(struct inode *inode,
+ struct writeback_control *wbc,
+ unsigned long nr_to_write),
+ TP_ARGS(inode, wbc, nr_to_write)
+);
+
+DEFINE_EVENT(writeback_single_inode_template, writeback_single_inode,
+ TP_PROTO(struct inode *inode,
+ struct writeback_control *wbc,
+ unsigned long nr_to_write),
+ TP_ARGS(inode, wbc, nr_to_write)
+);
+
#endif /* _TRACE_WRITEBACK_H */

/* This part must be outside protection */
--- linux-next.orig/fs/fs-writeback.c 2011-05-24 11:17:25.000000000 +0800
+++ linux-next/fs/fs-writeback.c 2011-05-24 11:17:26.000000000 +0800
@@ -346,6 +346,7 @@ writeback_single_inode(struct inode *ino
struct writeback_control *wbc)
{
struct address_space *mapping = inode->i_mapping;
+ long nr_to_write = wbc->nr_to_write;
unsigned dirty;
int ret;

@@ -368,6 +369,8 @@ writeback_single_inode(struct inode *ino
*/
if (wbc->sync_mode != WB_SYNC_ALL) {
requeue_io(inode, wb);
+ trace_writeback_single_inode_requeue(inode, wbc,
+ nr_to_write);
return 0;
}

@@ -467,6 +470,7 @@ writeback_single_inode(struct inode *ino
}
}
inode_sync_complete(inode);
+ trace_writeback_single_inode(inode, wbc, nr_to_write);
return ret;
}




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