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

H.J. Lu hjl.tools@gmail.com
Thu Feb 22 11:43:00 GMT 2018

On Mon, Feb 19, 2018 at 8:39 AM, H.J. Lu <hjl.tools@gmail.com> wrote:
> On Mon, Feb 19, 2018 at 7:53 AM, Michael Matz <matz@suse.de> wrote:
>> Hi,
>> On Mon, 19 Feb 2018, H.J. Lu wrote:
>>> This patch enables -z separate-code by default for x86.  To reduce
>>> x86-64 binary size, set ELF_MAXPAGESIZE to 4KB.
>> 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%.

>>> 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?

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