On Thu, May 12, 2011 at 09:57:22PM +0800, Wu Fengguang wrote:
> 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
>
> Signed-off-by: Wu Fengguang <fengguang.wu@xxxxxxxxx>
> ---
> fs/fs-writeback.c | 6 ++-
> include/trace/events/writeback.h | 56 +++++++++++++++++++++++++++++
> 2 files changed, 61 insertions(+), 1 deletion(-)
>
> --- linux-next.orig/include/trace/events/writeback.h 2011-05-12 11:46:27.000000000 +0800
> +++ linux-next/include/trace/events/writeback.h 2011-05-12 11:48:55.000000000 +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,
> @@ -201,6 +214,49 @@ DEFINE_EVENT(writeback_congest_waited_te
> TP_ARGS(usec_timeout, usec_delayed)
> );
>
> +TRACE_EVENT(writeback_single_inode,
> +
> + 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
> + )
> +);
> +
> #endif /* _TRACE_WRITEBACK_H */
>
> /* This part must be outside protection */
> --- linux-next.orig/fs/fs-writeback.c 2011-05-12 11:46:27.000000000 +0800
> +++ linux-next/fs/fs-writeback.c 2011-05-12 11:48:55.000000000 +0800
> @@ -356,6 +356,7 @@ 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;
>
> @@ -378,7 +379,8 @@ writeback_single_inode(struct inode *ino
> */
> if (wbc->sync_mode != WB_SYNC_ALL) {
> requeue_io(inode, wb);
> - return 0;
> + ret = 0;
> + goto out;
> }
>
> /*
> @@ -476,6 +478,8 @@ writeback_single_inode(struct inode *ino
> }
> }
> inode_sync_complete(inode);
> +out:
> + trace_writeback_single_inode(inode, wbc, nr_to_write);
> return ret;
> }
I think I'd prefer two separate trace calls rather than jumping to
one. That is, a trace_writeback_single_inode_requeue() event and a
trace_writeback_single_inode_done() event so we can see the separate
conditions in the trace....
Cheers,
Dave.
--
Dave Chinner
david@xxxxxxxxxxxxx
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