On Thu, 2011-08-18 at 17:48 +0800, Wu Fengguang wrote: > > For example, the user might want to write-back pages in smaller > > intervals to a block device which has a > > faster known writeback speed. > > That's not a complete rational. What does the user ultimately want by > setting a smaller interval? What would be the problems to the other > slow devices if the user does so by simply setting a small value > _globally_? > > We need strong use cases for doing such user interface changes. > Would you detail the problem and the pains that can only (or best) > be addressed by this patch? Here is a real use-case we had when developing the N900 phone. We had internal flash and external microSD slot. Internal flash is soldered in and cannot be removed by the user. MicroSD, in contrast, can be removed by the user. For the internal flash we wanted long intervals and relaxed limits to gain better performance. For MicroSD we wanted very short intervals and tough limits to make sure that if the user suddenly removes his microSD (users do this all the time) - we do not lose data. The discussed capability would be very useful in that case, AFAICS. IOW, this is not only about fast/slow devices and how quickly you want to be able to sync the FS, this is also about data integrity guarantees. -- Best Regards, Artem Bityutskiy -- 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
