On Thu, Mar 18, 2010 at 09:02:41PM -0700, David Miller wrote: > > Can we please remove the CALLER_ADDR0 et al. evaluations at the top > level in perf_fetch_caller_regs()? > > I take great pains to avoid having to flush the register windows on > sparc64 even when fetching callchains et al and any > __builtin_return_address() with an argument greater than zero is going > to force a register window flush to get emitted by gcc undoing all of > my hard work :-) > > You guys can put it into the x86 perf_fetch_caller_regs() or similar. > > If you need it to be evaluated at the call site, make the inline > overridable by the platform headers. > > I noticed that the powerpc assembler Paul posted the past few days > ignores this "ip" arg passed down and computes it by hand as it > walks up the stack chain in assembler. PowerPC therefore might be > getting similar inefficiences due to this CALLER_ADDR? stuff. Well, it would except that CALLER_ADDR1, 2, etc. turn into (0) on powerpc because we use the generic definition and we don't define CONFIG_FRAME_POINTER (it's meaningless on powerpc because the ABI defines that each stack frame always has a pointer to the previous frame). I should fix CALLER_ADDRx on powerpc one day, then we will have the extra inefficiency. Paul. -- 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
