This is the mail archive of the
libc-alpha@sourceware.org
mailing list for the glibc project.
Re: [PATCH] Add Prefer_MAP_32BIT_EXEC for Silvermont
- From: "H.J. Lu" <hjl dot tools at gmail dot com>
- To: Florian Weimer <fweimer at redhat dot com>
- Cc: Jeff Law <law at redhat dot com>, Zack Weinberg <zackw at panix dot com>, Andi Kleen <andi at firstfloor dot org>, Adhemerval Zanella <adhemerval dot zanella at linaro dot org>, GNU C Library <libc-alpha at sourceware dot org>
- Date: Mon, 14 Dec 2015 09:10:30 -0800
- Subject: Re: [PATCH] Add Prefer_MAP_32BIT_EXEC for Silvermont
- Authentication-results: sourceware.org; auth=none
- References: <CAKCAbMhMArQ9wsXhw2y+Fvv+_3O5i4g8pdDQdWo6_1YxqfVxkQ at mail dot gmail dot com> <CAMe9rOrVjSnhp-EzmAnVBg10wbqk9U4n+hL-3xF5=DPZP5co1A at mail dot gmail dot com> <CAKCAbMhk69hUBbrQ=0j0NDYjRT6R-EK1+F43+Mmi9FwS7epexQ at mail dot gmail dot com> <CAKCAbMhA6x4r6Bhw8cnAavoWzjWsm6WM8JPzrnCsrqxbEswS_g at mail dot gmail dot com> <87egeszoq3 dot fsf at tassilo dot jf dot intel dot com> <CAKCAbMibxh54DGJ6p59ah6jQK=oFkH9LCZo0UDBefQeh1y-5eg at mail dot gmail dot com> <CAMe9rOoyc4MXVz74GmjViora-iCEKitQXbpX9EB+Ln1Q_DAD_A at mail dot gmail dot com> <CAKCAbMi_noBivP+ksLaotNtfEhGrtUuUacbnZgjMg5m0PfEniw at mail dot gmail dot com> <20151211222913 dot GT15533 at two dot firstfloor dot org> <566B55DF dot 2040200 at redhat dot com> <20151212001449 dot GU15533 at two dot firstfloor dot org> <CAKCAbMgcZKr8-i2XuhHAnk4nKpJnpWEqj1XNuygkNhYzXPb8hA at mail dot gmail dot com> <566B8008 dot 6010106 at redhat dot com> <CAMe9rOofj5_TQFcU695CbMmpqcULUgD4r0O9kY2+VmsNoPJx9A at mail dot gmail dot com> <566EDCFF dot 7040301 at redhat dot com>
On Mon, Dec 14, 2015 at 7:15 AM, Florian Weimer <fweimer@redhat.com> wrote:
> On 12/12/2015 06:36 PM, H.J. Lu wrote:
>
>> Here is the updated patch to make it opt-in. OK for master?
>
> I would still like to see performance numbers for the PIE and vDSO
> cases, as requested here:
This optimization has no performance impact on PIE nor
vDSO.
> <https://sourceware.org/ml/libc-alpha/2015-12/>
>
> As far as I can tell, the application impact of this setting has not
> been investigated, either:
>
> <https://sourceware.org/ml/libc-alpha/2015-12/msg00261.html>
>
> And it probably makes sense to guard this by a configure switch because
> for almost all users, it's just bloat.
Adding a configure switch defeats LD_ENABLE_PREFER_MAP_32BIT_EXEC.
old:
[hjl@gnu-6 build-x86_64-linux]$ size elf/dl-sysdep.os
text data bss dec hex filename
3976 20 4 4000 fa0 elf/dl-sysdep.os
and new:
[hjl@gnu-6 build-x86_64-linux]$ size elf/dl-sysdep.os
text data bss dec hex filename
4201 20 4 4225 1081 elf/dl-sysdep.os
It increases elf/dl-sysdep.os by 225 bytes. Calling it "bloat" is
a stretch.
> I'm somewhat sympathetic to Zack's request to remove the special-casing
> on CPU settings. It would certainly simplify application compatibility
> testing without access to the defective silicon.
>
> Florian
>
--
H.J.