On Mon, 20 Mar 2023 at 22:30, Jonathan Wakely via Libstdc++ <
libstdc++@gcc.gnu.org> wrote:

> On 20/03/23 22:27 +0000, Jonathan Wakely wrote:
> >On 06/03/23 20:52 +0100, Jannik Glückert wrote:
> >>we were previously only using sendfile for files smaller than 2GB, as
> >>sendfile needs to be called repeatedly for files bigger than that.
> >>
> >>some quick numbers, copying a 16GB file, average of 10 repetitions:
> >>   old:
> >>       real: 13.4s
> >>       user: 0.14s
> >>       sys : 7.43s
> >>   new:
> >>       real: 8.90s
> >>       user: 0.00s
> >>       sys : 3.68s
> >>
> >>Additionally, this fixes
> >>https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108178
> >>
> >>libstdc++-v3/ChangeLog:
> >>
> >>       * acinclude.m4 (_GLIBCXX_HAVE_LSEEK): define
> >>       * config.h.in: Regenerate.
> >>       * configure: Regenerate.
> >>       * src/filesystem/ops-common.h: enable sendfile for files
> >>         >2GB in std::filesystem::copy_file, skip zero-length files
>
> Also, the ChangeLog entry needs to be indented with tabs, name the
> changed functions, and should be complete sentences, e.g.
>
>         * acinclude.m4 (_GLIBCXX_HAVE_LSEEK): Define.
>         * config.h.in: Regenerate.
>         * configure: Regenerate.
>         * src/filesystem/ops-common.h (copy_file_sendfile): Define new
>         function for sendfile logic. Loop to support large files. Skip
>         zero-length files.
>         (do_copy_file): Use it.
>
>
Here's what I plan to commit in a few weeks when GCC 14 Stage 1 opens.