Hi Hin-Tak, On Oct 7, 2012, at 3:21 AM, Hin-Tak Leung wrote: > Hi all, > > Currently debugging statements for the HFS+ driver are enabled/disabled at compiled time by modifying DBG_MASK towards the top of linux/fs/hfsplus/hfsplus_fs.h. > > Is there a strong reason against converting that to use the dynamic debug feature (linux/Documentation/dynamic-debug-howto.txt) instead? I assume there is a performance penalty for dynamic debugging vs compile-time config, and file system is probably one area where performance is important. So the other question is, does anybody know what sort of performance penality it makes? > I think that it is a good idea to use dynamic debug feature. It needs to make some modifications in HFS+ driver for this. As I can understand, disabled dynamic debug hasn't any performance penalty. But you will have a some performance degradation in the case of enabling dynamic debug. But it needs to take into consideration a concrete issue for making decision about how critical may using of dynamic debug. For example, the using of dynamic debug feature can completely hide issue reproducibility in the case of lock issue investigation. > One small reason I am thinking of converting is every time one adds a feature (like Vyacheslav's recent xttr patch series), one adds a bit mask. That obviously colides with outside-kernel patches like the journalling ones, since everybody uses the next-available bit. > The bit mask is a way of getting debug output for some HFS+ driver's feature. But dynamic debug can be a more flexible way of getting debug output, as I can understand. So, it makes sense to do the HFS+ driver modification for dynamic debug support. :-) With the best regards, Vyacheslav Dubeyko. > Other than dynamic-debugging, is there a better way of handling the debugging statements in the hfsplus driver, than it is currently doing? > > Hin-Tak -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
