From: Denys Vlasenko <vda.linux@xxxxxxxxxxxxxx> Date: Thu, 26 Jun 2008 05:35:59 +0200 > On Thursday 26 June 2008 02:28, David Miller wrote: > > From: Denys Vlasenko <vda.linux@xxxxxxxxxxxxxx> > > Date: Wed, 25 Jun 2008 22:37:58 +0200 > > > > Sparc64 has register windows: it passes arguments in registers, but it > > > > must allocate space for that registers. If the call stack is too deep (8 > > > > levels), the CPU runs out of registers and starts spilling the registers > > > > of the function 8-levels-deep to the stack. > > > > > > > > The stack usage could be reduced to 176 bytes with little work from gcc > > > > developers and to 128 bytes with more work (ABI change). If you wanted to > > > > > > Wow, it's nearly x2 reduction. > > > > > > ABI change in not a problem for kernel, since it is a "freestanding > > > application". Exactly like i386 switched to regparm, which is a different ABI. > > > > Except that nobody has written this code and therefore being about to > > use this unimplemented compiler facility to get correctness is not > > tenable. > > Inlining everything is even less tenable. I never suggested this. Although I do support inlining the cases which merely adjust the ordering of arguments being passed to function calls, because such inlines are essentially of zero cost and of gain to all platforms. > I am all for fixing code where there are extra useless levels of calls, > but in this example I pointed out that patch adds inlines too liberally. > Do you agree that blowing up every wake_up_bit() into half a dozen > or more C lines is not what we want? I stated my suggested alternative to this in another posting, so of course I do not support it as-is. -- To unsubscribe from this list: send the line "unsubscribe sparclinux" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
