Re: tracepoints in ext4 (and/or ext3?)

[Theodore Tso <tytso@mit.edu>]

On Tue, Aug 12, 2008 at 08:19:54AM -0500, Jose R. Santos wrote:
> 
> Good idea, although Im not sure if ext[34] is the best place we should
> start putting markers though.

I can think of ext3/4 specific markers that would be useful for people
who are tuning our filesystems for performance.  This would include
when we start and end tranactions, when we force a checkpoint, when we
create and, extend, and finish using a handle in the jbd layer.

In the ext4 itself, knowing when we are mapping delayed allocations
would be useful, as well as when we freeze and unfreeze a filesystem
(i.e., for snapshots).

There are a lot of other tracepoints that probably do make more sense
to be put in the VFS layer, although on thing that would be *really*
nice is some semantic sugar in Systemtap or in a Systemtap tapset so
that we only trigger the tracepoints for a particular filesystem.

     	     	     	 	     	   - Ted