On Wed, Sep 14, 2016 at 4:06 AM, Jonathan Wakely <jwak...@redhat.com> wrote: > On 13/09/16 11:02 -0700, Cong Wang wrote: >> >> In !_GLIBCXX_USE_CXX11_ABI implementation, string::clear() calls >> _M_mutate(), which could allocate memory as we do COW. This hurts >> performance when string::clear() is on the hot path. >> >> This patch improves it by using _S_empty_rep directly when >> _GLIBCXX_FULLY_DYNAMIC_STRING is not enabled. And Linux distro like >> Fedora doesn't enable this, this is why we caught it. >> >> The copy-and-clear test shows it improves by 50%. >> >> Ran all testsuites on Linux-x64. > > > Thank you for the patch (and changelog and test results!). > > Do you have a GCC copyright assignment in place? See > https://gcc.gnu.org/contribute.html#legal for details.
Oh, didn't notice this, I thought gcc has something as quick as the 'Signed-off-by' for Linux kernel (I am a Linux kernel developer). I will do it. > > If I understand the purpose of the change correctly, it's similar to > https://gcc.gnu.org/ml/gcc-patches/2014-06/msg00278.html - is that > right? > Oh, yes, I didn't know your patch because I don't subscribe gcc mailing list. I am wondering why your patch is not merged after 2+ years? Please let me know what you prefer: 1) You update your patch and get it merged; 2) Use my patch if it looks good. I am fine with either way. :) Thanks.
