Messages in this thread | | | Date | Tue, 13 Jan 2009 10:17:39 +0100 | From | Frederic Weisbecker <> | Subject | Re: [PATCH] rcu: convert rcupreempt trace to seq file |
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On Tue, Jan 13, 2009 at 05:03:05PM +0800, Li Zefan wrote: > Frederic Weisbecker wrote: > > On Tue, Jan 13, 2009 at 11:19:44AM +0800, Li Zefan wrote: > >>> 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. > >>> > >> Hi Frederic, > >> > >> I've converted rcupreempt to use trace points, but I don't see much advantage to use > >> trace stat instead of using seq_file directly.. And can you add support to allow > >> me to provide stat_show() only ? I think it's common that the stat file has only > >> one entry. > >> > >> > >> Regards > >> Li Zefan > > > > > > It simplifies (I hope) a bit the seqfile. > > The interface is very similar except that you don't need to deal > > with debugfs stuffs, sorting, and position inside the seqfile. > > And it unifies the stat files into a common directory instead of > > having them grained into a mess of debugfs filesystem.... > > > > OK. It makes things easier for some cases. :) > > But will trace_stat/ become a mess when there are many stat files in it ? > > Does it make sense to support making subdir in trace_stat/ ?
Yes it's on my projects :-)
> > I could let it handle only stat_show when you have only one entry but that > > would break the sense of stat_show. > > If it's so common to have only one stat entry, perhaps I could provide a special callback > > for that, something like stat_show_unique()... > > > > Hm? > > > > stat_show_single() ? I don't know which name is better. > > Like it's common to use single_open with seq_file, I think it's needed as we add more > stat files into trace_stat. > > Regards > Li Zefan >
stat_show_single() is a better name. Yes that makes sense, I will add this callback.
Thanks.
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