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>
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index f43c479..5185fad 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -346,6 +346,7 @@
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 @@
*/
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 @@
}
}
inode_sync_complete(inode);
+ trace_writeback_single_inode(inode, wbc, nr_to_write);
return ret;
}