Messages in this thread | | | Subject | Re: [RFC PATCH] seq_file: Use seq_puts when seq_printf has only a format with no args | From | Joe Perches <> | Date | Sat, 16 Mar 2013 10:51:18 -0700 |
| |
On Sat, 2013-03-16 at 09:43 -0600, Bjorn Helgaas wrote: > On Sat, Mar 16, 2013 at 7:50 AM, Joe Perches <joe@perches.com> 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. > > This is certainly a neat trick. > > But I don't really like the fact that it complicates things for every > future code reader, especially when a trivial change in the caller > would accomplish the same thing. Do you have any idea how much > performance we would gain in exchange for the complication?
Nope. I believe it's trivial in any case. I just saw Steven's trace hack and thought of seq_printk.
Is there a real performance sensitive seq_printf anywhere?
It's trivial to replace seq_printf("constant") with seq_puts but there are over a thousand of them.
It may be better to just leave everything as-is.
| |