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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: Wu Fengguang <fengguang.wu@intel.com>
This commit is contained in:
Wu Fengguang 2011-04-23 12:27:27 -06:00
parent 251d6a471c
commit e84d0a4f8e
2 changed files with 35 additions and 4 deletions
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12
fs/fs-writeback.c
View File

@ -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)

25
include/trace/events/writeback.h
View File

@ -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),