On Wed, Feb 26, 2014 at 12:14 PM, David Ahern <dsah...@gmail.com> wrote: > On 2/26/14, 12:25 PM, Andy Lutomirski wrote: >> >> On Wed, Feb 26, 2014 at 11:19 AM, David Ahern <dsah...@gmail.com> wrote: >>> >>> On 2/26/14, 11:59 AM, Andy Lutomirski wrote: >>> >>>> I wonder if anyone who uses perf for userspace profiling *ever* uses >>>> FP and gets away with it. There's precious little userspace software >>>> compiled with frame pointers these days on most architectures. >>> >>> >>> >>> yes and yes. With control over the entire stack we are making sure >>> frame-pointers are enabled as much as possible. >>> >> >> I'm curious why. > > > Is there some reason not to enable frame pointers?
Speed. FPO saves one register (a big deal on x86_32; not so important on x86_64) but also saves a few cycles on function entry and exit, which is a bigger deal for small functions. > > fp method has much less overhead than dwarf, and good, clear callchains are > important. > Agreed about the good, clear callchains. But DWARF seems to work pretty well, and you only have the overhead when you're actually debugging or profiling. > >> >> Maybe this should be a config option. Anyone using a standard distro >> is running a nearly completely frame-pointer-omitted userspace these >> days. > > > Does WRL or Yocto fall into that 'standard distro' comment? Fairly easy to > enable frame-pointers. Fair enough :) --Andy -- 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/