>> Calling the function "seq_putc" will be more efficient than "seq_printf" >> in this case because of the following reasons. >> >> 1. How does the distribution look like for supported processor architectures >> where the data transfer for bytes (as a function call parameter) >> is faster than for (string) pointers? >> > How would I know? How many processor architecture characteristics do you know already? * Is a string pointer often longer than a byte? * I imagine that it can become also interesting to check byte level data access under constraints of machine word sizes and alignment. > I would assume that _you_ did some measurements here; How much would you trust in any concrete numbers I could present for this use case? Do you give more trust to a reference testing platform? > I could easily claim that seq_printf() is more efficient than > seq_putc(), and won't apply your patch. This is also possible in principle. > So _you_ have to prove that your patch is more efficient. How many results would we like to clarify from various hardware and software combinations? >> 2. Did anybody measure already how many the execution times can vary >> for these functions? >> > Probably not. Thanks for this information. How important are the mentioned functions for you within the Linux programming interface so far? > Unless _you_ prove that _your_ patch is more efficient it won't get applied. Which data would you accept as a "prove" in this case? >> Where do you get doubts about its efficiency for the data processing >> of a single character? >> > Because it's being called at the end of a function calling seq_printf() already. Interesting view … > So exchanging a single call is probably not helping anything, > as the compiler will optimize it anyway. How common is the discussed software transformation between implementations for optimising compilers? > Case in point: with your patch the x86_64 compiler generates nearly > identical code for driver/md/raid1.c, but with one instruction _more_ > after your patch has been applied. Which software versions and command parameters did you try out for this information (from an unspecified run time environment)? > So it's not immediately obvious that your patch is an improvement. I agree that there are system properties and constraints which can be considered further. Regards, Markus -- To unsubscribe from this list: send the line "unsubscribe kernel-janitors" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
