On Mon, Nov 01, 2010 at 11:21:50PM +0800, Christoph Hellwig wrote:
> > +static void _bdi_wakeup_flusher(struct backing_dev_info *bdi)
>
> Remove the leading underscore, please.
OK, makes sense. The updated patch will follow.
> > void bdi_start_background_writeback(struct backing_dev_info *bdi)
> > {
> > - __bdi_start_writeback(bdi, LONG_MAX, true, true);
> > + /*
> > + * We just wake up the flusher thread. It will perform background
> > + * writeback as soon as there is no other work to do.
> > + */
> > + spin_lock_bh(&bdi->wb_lock);
> > + _bdi_wakeup_flusher(bdi);
> > + spin_unlock_bh(&bdi->wb_lock);
>
> We probably want a trace point here, too.
>
> Otherwise the patch looks good to me. Thanks for bringing it up again.
Thanks. It's trivial to add the trace point, here is the incremental
patch.
Thanks,
Fengguang
---
writeback: trace wakeup event for background writeback
This tracks when balance_dirty_pages() tries to wakeup the flusher
thread for background writeback (if it was not started already).
Signed-off-by: Wu Fengguang <fengguang.wu@xxxxxxxxx>
---
fs/fs-writeback.c | 1 +
include/trace/events/writeback.h | 1 +
2 files changed, 2 insertions(+)
--- linux-next.orig/include/trace/events/writeback.h 2010-11-02 04:17:26.000000000 +0800
+++ linux-next/include/trace/events/writeback.h 2010-11-02 04:21:02.000000000 +0800
@@ -81,6 +81,7 @@ DEFINE_EVENT(writeback_class, name, \
TP_ARGS(bdi))
DEFINE_WRITEBACK_EVENT(writeback_nowork);
+DEFINE_WRITEBACK_EVENT(writeback_wake_background);
DEFINE_WRITEBACK_EVENT(writeback_wake_thread);
DEFINE_WRITEBACK_EVENT(writeback_wake_forker_thread);
DEFINE_WRITEBACK_EVENT(writeback_bdi_register);
--- linux-next.orig/fs/fs-writeback.c 2010-11-02 04:22:17.000000000 +0800
+++ linux-next/fs/fs-writeback.c 2010-11-02 04:22:33.000000000 +0800
@@ -164,6 +164,7 @@ void bdi_start_background_writeback(stru
* We just wake up the flusher thread. It will perform background
* writeback as soon as there is no other work to do.
*/
+ trace_writeback_wake_background(bdi);
spin_lock_bh(&bdi->wb_lock);
bdi_wakeup_flusher(bdi);
spin_unlock_bh(&bdi->wb_lock);
--
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