This is the mail archive of the glibc-bugs@sourceware.org mailing list for the glibc project.


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

[Bug dynamic-link/19367] Improve branch prediction on Silvermont


https://sourceware.org/bugzilla/show_bug.cgi?id=19367

--- Comment #3 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> ---
This is an automated email from the git hooks/post-receive script. It was
generated because a ref change was pushed to the repository containing
the project "GNU C Library master sources".

The branch, hjl/32bit/2.22 has been created
        at  e4c29a1d3f7d96683582b7dbd86fb8d1ac707ea6 (commit)

- Log -----------------------------------------------------------------
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=e4c29a1d3f7d96683582b7dbd86fb8d1ac707ea6

commit e4c29a1d3f7d96683582b7dbd86fb8d1ac707ea6
Author: H.J. Lu <hjl.tools@gmail.com>
Date:   Wed Oct 21 14:44:23 2015 -0700

    Add Prefer_MAP_32BIT_EXEC to map executable pages with MAP_32BIT

    According to Silvermont software optimization guide, for 64-bit
    applications, branch prediction performance can be negatively impacted
    when the target of a branch is more than 4GB away from the branch.  Add
    the Prefer_MAP_32BIT_EXEC bit so that mmap will try to map executable
    pages with MAP_32BIT first.  NB: MAP_32BIT will map to lower 2GB, not
    lower 4GB, address.  Prefer_MAP_32BIT_EXEC reduces bits available for
    address space layout randomization (ASLR), which is always disabled for
    SUID programs and can only be enabled by setting environment variable,
    LD_PREFER_MAP_32BIT_EXEC.

    On Fedora 23, this patch speeds up GCC 5 testsuite by 3% on Silvermont.

        [BZ #19367]
        * sysdeps/unix/sysv/linux/wordsize-64/mmap.c: New file.
        * sysdeps/unix/sysv/linux/x86_64/64/dl-librecon.h: Likewise.
        * sysdeps/unix/sysv/linux/x86_64/64/mmap.c: Likewise.
        * sysdeps/x86/cpu-features.h (bit_Prefer_MAP_32BIT_EXEC): New.
        (index_Prefer_MAP_32BIT_EXEC): Likewise.

    (cherry picked from commit b9eb92ab05204df772eb4929eccd018637c9f3e9)

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=e7b516ad591913995b928ce6db296e2c57a099e4

commit e7b516ad591913995b928ce6db296e2c57a099e4
Author: H.J. Lu <hjl.tools@gmail.com>
Date:   Tue Dec 15 11:46:54 2015 -0800

    Enable Silvermont optimizations for Knights Landing

    Knights Landing processor is based on Silvermont.  This patch enables
    Silvermont optimizations for Knights Landing.

        * sysdeps/x86/cpu-features.c (init_cpu_features): Enable
        Silvermont optimizations for Knights Landing.

    (cherry picked from commit c9afcaaafaf9126a973883528eed8d0058a264c0)

-----------------------------------------------------------------------

-- 
You are receiving this mail because:
You are on the CC list for the bug.

Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]