Re: RFC: x86: Enable -z separate-code by default

["H.J. Lu" <hjl dot tools at gmail dot com>]

On Thu, Feb 22, 2018 at 9:43 AM, H.J. Lu <hjl.tools@gmail.com> wrote:
> On Thu, Feb 22, 2018 at 6:25 AM, H.J. Lu <hjl.tools@gmail.com> wrote:
>> On Thu, Feb 22, 2018 at 5:22 AM, Michael Matz <matz@suse.de> wrote:
>>> Hi,
>>>
>>> On Thu, 22 Feb 2018, H.J. Lu wrote:
>>>
>>>> >> Meh :-( Have you done any performance measurements on, say, SPECcpu?
>>>> >
>>>> > We will.
>>>>
>>>> We compared SPEC CPU 2017 performance before and after this change on
>>>> Skylake server.  There are no any significant performance changes.
>>>> Everything is mostly below +/-1%.
>>>
>>> Thanks, seems fine.
>>>
>>>> >>> Should I add an ld configure option, --enable-separate-code, instead?
>>>> >>
>>>> >> Yes, definitely.  For old distros at least I definitely want to retain old
>>>> >> behaviour by default and a configure switch would make that easier.
>>>> >
>>>> > Will do.
>>>> >
>>>>
>>>> Here is the patch to add --enable-separate-code to ld configure and
>>>> enable it by default for Linux/x86.  But the default maximum page size
>>>> is changed to 4KB for x86-64.
>>>>
>>>> Any comments?
>>>
>>> Should the max page size setting (without override on cmdline) depend on
>>> separate-code, or not?  I'm split minds here, I'm worried that the 2mb
>>
>> I will give it a try.
>>
>
> Here is the patch which sets maximum page size to 2MB page size when
> -z separate-code is disabled by default.
>

I am checking in this patch.

-- 
H.J.