Messages in this thread |  | | | Date | Tue, 13 Jan 2009 17:03:05 +0800 | | From | Li Zefan <> | | Subject | Re: [PATCH] rcu: convert rcupreempt trace to seq file |
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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/ ?
> 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
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