Messages in this thread | | | Date | Sun, 11 Jan 2009 06:01:31 +0100 | From | Frederic Weisbecker <> | Subject | Re: [PATCH] rcu: convert rcupreempt trace to seq file |
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On Sun, Jan 11, 2009 at 02:39:40AM +0100, Ingo Molnar wrote: > > * Paul E. McKenney <paulmck@linux.vnet.ibm.com> wrote: > > > On Sat, Jan 10, 2009 at 03:48:46PM +0800, Li Zefan wrote: > > > Impact: also fix a bug in show_rcustats() > > > > > > Use seq file for simplification, and the global buffer and mutex can be > > > removed. > > > > Looks very good, and passes my tests. > > > > > While doing this, I found rcustats will never show 'ggp' and 'rcc' fields > > > due to a bug in show_rcustats(). > > > > Good eyes! > > > > The only change I ask is that you pull the contents of > > rcupreempt_debugfs_init() into the now-one-line rcupreempt_trace_init(). > > > > With that change: > > > > Tested-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> > > Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> > > > > > --- > > > kernel/rcupreempt_trace.c | 155 ++++++++++++++++++++------------------------- > > i think the whole kernel/rcupreempt_trace.c file might be a good candidate > for the 'statistical tracing' extensions to ftrace that Frederice is > working on. > > That way there would just be a few tracepoints, and the rest would be done > in kernel/tracing/trace_rcupreempt.c, or so. > Ingo
Indeed!
The debugfs and seqfile handling and handled in the statistical tracing engine.
You just have to provide an iterator for your stat entries through two callbacks:
_ stat_start() -> gives the first entry _ stat_next() -> iterates over the next entry
And an output callback
_ stat_show() -> print one entry from your stat list
And two optional things:
_ stat_cmp() -> compare two entries, useful if you want your stats to be sorted _ stat_headers() -> provide the first line in your stat file, typically to describe your columns
The last thing you need is to give a name to your trace file. You will retrieve it into /debugfs/tracing/trace_stat/your_file_name as a current snapshot of your stats.
It is currently used by the branch tracer, and by a pending patch for a new workqueue tracer which will provide you a simple example.
If you have any question about how to use it, don't hesitate to ask.
Frederic.
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