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SubjectRe: [PATCH 16/17] writeback: trace event writeback_single_inode
On Mon, May 16, 2011 at 08:14:48AM +0800, Dave Chinner wrote:
> On Fri, May 13, 2011 at 01:37:00PM +0800, Wu Fengguang wrote:
> > On Fri, May 13, 2011 at 07:20:51AM +0800, Dave Chinner wrote:
> > > 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@intel.com>
> > > > ---
> > > > 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....
> >
> > The requeue events are likely to disappear when IO-less
> > balance_dirty_pages() are upstream. Do you still feel like adding a
> > trace for it?
>
> Requeue events are not specific to balance_dirty_pages() based
> writeback. background/kupdate writeback can trigger them because a
> sync write, fsync or sync is in progress. So yes, please add a
> separate trace for it.

OK, here is the incremental change.

I noticed that I_SYNC won't be set in fsync, but could possibly be set
outside of the flusher thread via write_inode_now() and sync_inode().

Thanks,
Fengguang
---

fs/fs-writeback.c | 5 +++--
include/trace/events/writeback.h | 16 +++++++++++++++-
2 files changed, 18 insertions(+), 3 deletions(-)

--- linux-next.orig/fs/fs-writeback.c 2011-05-16 20:12:04.000000000 +0800
+++ linux-next/fs/fs-writeback.c 2011-05-16 20:12:08.000000000 +0800
@@ -385,8 +385,9 @@ writeback_single_inode(struct inode *ino
*/
if (wbc->sync_mode != WB_SYNC_ALL) {
requeue_io(inode, wb);
- ret = 0;
- goto out;
+ trace_writeback_single_inode_requeue(inode, wbc,
+ nr_to_write);
+ return 0;
}

/*
--- linux-next.orig/include/trace/events/writeback.h 2011-05-16 20:12:26.000000000 +0800
+++ linux-next/include/trace/events/writeback.h 2011-05-16 20:15:42.000000000 +0800
@@ -239,7 +239,7 @@ DEFINE_EVENT(writeback_congest_waited_te
TP_ARGS(usec_timeout, usec_delayed)
);

-TRACE_EVENT(writeback_single_inode,
+DECLARE_EVENT_CLASS(writeback_single_inode_template,

TP_PROTO(struct inode *inode,
struct writeback_control *wbc,
@@ -282,6 +282,20 @@ TRACE_EVENT(writeback_single_inode,
)
);

+DEFINE_EVENT(writeback_single_inode_template, writeback_single_inode_requeue,
+ TP_PROTO(struct inode *inode,
+ struct writeback_control *wbc,
+ unsigned long nr_to_write),
+ TP_ARGS(inode, wbc, nr_to_write)
+);
+
+DEFINE_EVENT(writeback_single_inode_template, writeback_single_inode,
+ TP_PROTO(struct inode *inode,
+ struct writeback_control *wbc,
+ unsigned long nr_to_write),
+ TP_ARGS(inode, wbc, nr_to_write)
+);
+
#endif /* _TRACE_WRITEBACK_H */

/* This part must be outside protection */

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