[PATCH] Add Prefer_MAP_32BIT_EXEC for Silvermont

[H.J. Lu]

On Fri, Dec 11, 2015 at 1:16 PM, Zack Weinberg <zackw@panix.com> wrote:
>
>> Also 3% (likely more in other workloads) is a significant performance
>> difference, especially when we're talking about something as common as
>> function calls.
>
> I saw a claim of 3% *overall* performance increase on an artificial
> benchmark and that's all.  I currently suspect this will turn out to
> be unmeasurable on realistic workloads.

3% speedup is for my typical workloads, which is running GCC.   For
an artificial benchmark, I got

Old glibc:

[hjl@gnu-slm-1 dlcall]$
/export/build/gnu/glibc/build-x86_64-linux.old/elf/ld-linux-x86-64.so.2
--library-path /export/build/gnu/glibc/build-x86_64-linux
intel64/dlcall

Time for 1000000 calls into dynamic library   1.00   ,  22.83 MT,
22.83 MT,  22.83 MT,       0 T

New glibc:

[hjl@gnu-slm-1 dlcall]$
/export/build/gnu/glibc/build-x86_64-linux/elf/ld-linux-x86-64.so.2
--library-path /export/build/gnu/glibc/build-x86_64-linux
intel64/dlcall

Time for 1000000 calls into dynamic library   1.00   ,   2.87 MT,
2.87 MT,   2.87 MT,       0 T

which is 8X speedup.


-- 
H.J.