[PATCH] x86: Add thresholds for "rep movsb/stosb" to tunables

[Florian Weimer]

* H. J. Lu via Libc-alpha:

> On Mon, Jun 1, 2020 at 1:15 PM H.J. Lu <hjl.tools@gmail.com> wrote:
>>
>> On Mon, Jun 1, 2020 at 12:38 PM Carlos O'Donell <carlos@redhat.com> wrote:
>> >
>> > On Mon, Jun 1, 2020 at 3:33 PM H.J. Lu <hjl.tools@gmail.com> wrote:
>> > > Did you mean adding  --list-tunables to ld.so?  libc.so.6 doesn't take
>> > > any arguments.
>> >
>> > Yes, I mean adding argument processing to libc.so.6, and handling
>> > --list-tunables.
>> >
>> > We have enough infrastructure in place that wiring that up shouldn't be too bad?
>> >
>> > Then, even in trimmed down containers, you can just run
>> > /lib64/libc.so.6 --list-tunables and get back the list of tunables and
>> > their min, max, and security values.
>>
>> Adding an argument to libc.so.6 is difficult since argument passing is
>> processor specific.  Adding --list-tunables to ld.so is more doable.
>
> But tunables are in libc.so.

If this is really a problem, we can load libc.so and call a
GLIBC_PRIVATE function to print the information.