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Commit e84d0a4f authored by Wu Fengguang's avatar Wu Fengguang
Browse files

writeback: trace event writeback_queue_io 



Note that it adds a little overheads to account the moved/enqueued
inodes from b_dirty to b_io. The "moved" accounting may be later used to
limit the number of inodes that can be moved in one shot, in order to
keep spinlock hold time under control.

Signed-off-by: default avatarWu Fengguang <fengguang.wu@intel.com>
parent 251d6a47

fs/fs-writeback.c

+10 −4
Original line number Diff line number Diff line
@@ -248,7 +248,7 @@ static bool inode_dirtied_after(struct inode *inode, unsigned long t) 
/*

 * Move expired dirty inodes from @delaying_queue to @dispatch_queue.

 */

static void move_expired_inodes(struct list_head *delaying_queue,

static int move_expired_inodes(struct list_head *delaying_queue,

			       struct list_head *dispatch_queue,

			       unsigned long *older_than_this)

{
@@ -257,6 +257,7 @@ static void move_expired_inodes(struct list_head *delaying_queue, 
	struct super_block *sb = NULL;

	struct inode *inode;

	int do_sb_sort = 0;

	int moved = 0;



	while (!list_empty(delaying_queue)) {

		inode = wb_inode(delaying_queue->prev);
@@ -267,12 +268,13 @@ static void move_expired_inodes(struct list_head *delaying_queue, 
			do_sb_sort = 1;

		sb = inode->i_sb;

		list_move(&inode->i_wb_list, &tmp);

		moved++;

	}



	/* just one sb in list, splice to dispatch_queue and we're done */

	if (!do_sb_sort) {

		list_splice(&tmp, dispatch_queue);

		return;

		goto out;

	}



	/* Move inodes from one superblock together */
@@ -284,6 +286,8 @@ static void move_expired_inodes(struct list_head *delaying_queue, 
				list_move(&inode->i_wb_list, dispatch_queue);

		}

	}

out:

	return moved;

}



/*
@@ -299,9 +303,11 @@ static void move_expired_inodes(struct list_head *delaying_queue, 
 */

static void queue_io(struct bdi_writeback *wb, unsigned long *older_than_this)

{

	int moved;

	assert_spin_locked(&wb->list_lock);

	list_splice_init(&wb->b_more_io, &wb->b_io);

	move_expired_inodes(&wb->b_dirty, &wb->b_io, older_than_this);

	moved = move_expired_inodes(&wb->b_dirty, &wb->b_io, older_than_this);

	trace_writeback_queue_io(wb, older_than_this, moved);

}



static int write_inode(struct inode *inode, struct writeback_control *wbc)

include/trace/events/writeback.h

+25 −0
Original line number Diff line number Diff line
@@ -162,6 +162,31 @@ DEFINE_WBC_EVENT(wbc_balance_dirty_written); 
DEFINE_WBC_EVENT(wbc_balance_dirty_wait);

DEFINE_WBC_EVENT(wbc_writepage);



TRACE_EVENT(writeback_queue_io,

	TP_PROTO(struct bdi_writeback *wb,

		 unsigned long *older_than_this,

		 int moved),

	TP_ARGS(wb, older_than_this, moved),

	TP_STRUCT__entry(

		__array(char,		name, 32)

		__field(unsigned long,	older)

		__field(long,		age)

		__field(int,		moved)

	),

	TP_fast_assign(

		strncpy(__entry->name, dev_name(wb->bdi->dev), 32);

		__entry->older	= older_than_this ?  *older_than_this : 0;

		__entry->age	= older_than_this ?

				  (jiffies - *older_than_this) * 1000 / HZ : -1;

		__entry->moved	= moved;

	),

	TP_printk("bdi %s: older=%lu age=%ld enqueue=%d",

		__entry->name,

		__entry->older,	/* older_than_this in jiffies */

		__entry->age,	/* older_than_this in relative milliseconds */

		__entry->moved)

);



DECLARE_EVENT_CLASS(writeback_congest_waited_template,



	TP_PROTO(unsigned int usec_timeout, unsigned int usec_delayed),