On Wed, Sep 05, 2012 at 10:01:37PM +0100, Catalin Marinas wrote: > There are indeed a few KB gain in code size but that's probably coming > from the exception table since otherwise you just replace a bl with > ldrt. It depends on what the compiler does as well, the arm code has > some carefully chosen registers when calling the __get_user_x function. It's more than that - it's not just the ldr but also a zeroing of a temporary register to hold the error code should the instruction fault. So it's not only the exception tables but also an increase in the main path - and that's where you benefit from having it out of line and thereby a hotter i-cache. > If you do the access_ok inline and the __get_user_x separately, the size > increase is even greater (at least in the arm64 case it can get to over > 20KB). I think x86 does the access_ok check out of line. Please talk to Will about get_user() and put_user(). Afterwards you will definitely want to keep them out of line on 64-bit ARM. -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
