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Re: [PATCH] Add Prefer_MAP_32BIT_EXEC for Silvermont
- From: "H.J. Lu" <hjl dot tools at gmail dot com>
- To: Zack Weinberg <zackw at panix dot com>
- Cc: 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: Fri, 11 Dec 2015 13:25:17 -0800
- Subject: Re: [PATCH] Add Prefer_MAP_32BIT_EXEC for Silvermont
- Authentication-results: sourceware.org; auth=none
- References: <20151211143706 dot GA7868 at intel dot com> <alpine dot DEB dot 2 dot 10 dot 1512111539300 dot 17023 at digraph dot polyomino dot org dot uk> <CAMe9rOqbqyFw3CMa35vwOEefdFq1xK2Q9hX8GXoGMKVZ-A2y0g at mail dot gmail dot com> <566AF894 dot 4060300 at linaro dot org> <CAMe9rOr-LypZXvq4Y4uwE_JybYoTXctZXMLjo4TH517NnC6omg at mail dot gmail dot com> <566B01BE dot 1070703 at linaro dot org> <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>
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.