Build glibc for aarch64 with C-only versions of memcpy?

[Miller, Tim]

On 12/15/21, 3:41 PM, "Florian Weimer" <fweimer@redhat.com> wrote:

    * Tim via Libc-help Miller:

    > I am doing some software profiling on an aarch64 system, and I’m using
    > the Linux perf tool. The problem I’m running into is that
    > “__GI___memcpy_simd” keeps showing up as the function with the most
    > CPU usage.

    This sounds like a perf bug.  Surely it can look at the LR register and
    see where the call is coming from?

Are you referring to the LBR mode that perf supports? When I try to select that I get this error:

Error:
PMU Hardware doesn't support sampling/overflow-interrupts.

    If it shows up so high in profiles, I suggest to attach a debugger and
    see if you can get to it to stop in the memcpy call, and take things
    from there.

It's not that high. It's 3 to 4 percent. But it's the top user and MAY be one of the things contributing to a 10% performance regression I'm seeing.

I'll try the debugger. Thanks!

    Thanks,
    Florian