Messages in this thread | | | Date | Sat, 16 Mar 2013 17:54:47 +0000 | From | Al Viro <> | Subject | Re: [RFC PATCH] seq_file: Use seq_puts when seq_printf has only a format with no args |
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On Sat, Mar 16, 2013 at 06:50:44AM -0700, Joe Perches wrote: > Instead of converting the 800 or so uses of seq_printf with > a constant format (without a % substitution) to seq_puts, > maybe there's another way to slightly speed up these outputs. > > Taking a similar approach to commit abd84d60eb > ("tracing: Optimize trace_printk() with one arg to use trace_puts()") > use the preprocessor to convert seq_printf(seq, "string constant") > to seq_puts(seq, "string constant") > > By stringifying __VA_ARGS__, we can, at compile time, determine > the number of args that are being passed to seq_printf() and > call seq_puts or seq_printf appropriately. > > The actual function definition for seq_printf must now > be enclosed in parenthesis to avoid further macro expansion.
Joe, would you mind showing me a single real-world case where that "optimization" would really matter? Adding a module that would produce a seq_file in procfs, with contents generated by something like for(i = 0; i < 4000; i++) seq_printf(m, "a"); and application that would keep reading that file in a loop does not count, TYVM. Until then, NAKed-by: Al Viro <viro@zeniv.linux.org.uk> NAKed-because: GAFL
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