Am 08.04.2015 um 15:16 schrieb Pengfei Yuan: > 2015-04-08 20:19 GMT+08:00 Richard Weinberger <richard.weinber...@gmail.com>: >> On Wed, Apr 8, 2015 at 3:00 AM, Pengfei Yuan <0xcool...@gmail.com> wrote: >>> Could you please provide some examples that I can investigate? >>> Thanks! >> >> It would be awesome if you could find out which gcc optimizations >> cause the speed up. >> "gcc -c -Q -O3 --help=optimizers" will help you. >> > > This is really helpful. > But I can only find very short description for each option from > https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html
Yeah, but if you know -fXY gives a nice speed up we can add it to our CFLAGS if it makes sense and has not much downsides. Blindly enabling -O3 can be dangerous as it might make the generated code much bigger and the asm unreadable. >> Please also double check your results. >> You need do to multiple runs, etc... >> Especially the redis speed up looks odd. Does redis really spend that much >> time >> in the kernel? > > Redis is special among the six applications because it is single-threaded. Still it would be nice to now much more about the load and why -O3 helps. Thanks, //richard -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
