On Fri 06-05-11 00:37:30, Wu Fengguang wrote:
> [changes from v1: due to concerns about the relative older_than_this,
> I added the raw older_than_this to the trace output. Hope the added
> overheads are not a big concern.]
>
> 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.
This is fine by me.
Honza
> ---
> fs/fs-writeback.c | 14 ++++++++++----
> include/trace/events/writeback.h | 25 +++++++++++++++++++++++++
> 2 files changed, 35 insertions(+), 4 deletions(-)
>
> --- linux-next.orig/fs/fs-writeback.c 2011-05-05 23:53:33.000000000 +0800
> +++ linux-next/fs/fs-writeback.c 2011-05-05 23:53:34.000000000 +0800
> @@ -258,15 +258,16 @@ static bool inode_dirtied_after(struct i
> /*
> * 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)
> + unsigned long *older_than_this)
> {
> LIST_HEAD(tmp);
> struct list_head *pos, *node;
> 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);
> @@ -277,12 +278,13 @@ static void move_expired_inodes(struct l
> 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 */
> @@ -294,6 +296,8 @@ static void move_expired_inodes(struct l
> list_move(&inode->i_wb_list, dispatch_queue);
> }
> }
> +out:
> + return moved;
> }
>
> /*
> @@ -309,9 +313,11 @@ static void move_expired_inodes(struct l
> */
> 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)
> --- linux-next.orig/include/trace/events/writeback.h 2011-05-05 23:53:33.000000000 +0800
> +++ linux-next/include/trace/events/writeback.h 2011-05-06 00:14:09.000000000 +0800
> @@ -158,6 +158,31 @@ DEFINE_WBC_EVENT(wbc_balance_dirty_writt
> 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),
--
Jan Kara <jack@xxxxxxx>
SUSE Labs, CR
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