On Feb 12, 2017, at 4:07 PM, Andrew Pinski [off-list ref] wrote:

On Mon, Jan 9, 2017 at 3:29 AM, Yury Norov [off-list ref] wrote:

quoted

This series enables aarch64 with ilp32 mode.

...

For folks concerned about performance, here is what we get for SPEC
CPU 2006 on ThunderX 2 CN99xx.
Positive means ILP32 is faster than LP64.  This core does not have
AARCH32 so I can't compare that.
Also my LP64 scores don't change with and without the patches.

Options:
-Ofast -flto=32 -mcpu=native -fno-aggressive-loop-optimizations
-funroll-loops -fprefetch-loop-arrays
GCC 7.0.1 r245361 with ilp32 multi-arch patch applied.
4.10rc2 Plus ILP32 patches

SPEC CPU 2006 INT ILP32/LP64
400.perlbench           5.23%
401.bzip2                  7.83%
403.gcc                     6.22%
429.mcf                     14.25%
445.gobmk                 -1.33%
456.hmmer                 -0.61%
458.sjeng                    0.00%
462.libquantum            -7.38%
464.h264ref                 10.86%
471.omnetpp               13.53%
473.astar                      1.38%
483.xalancbmk             3.73%
Score                            4.29%

Rate (32):
400.perlbench           6.10%
401.bzip2                  7.10%
403.gcc                     6.71%
429.mcf                     57.29%
445.gobmk                -0.87%
456.hmmer                -0.19%
458.sjeng                  0.22%
462.libquantum         0.00%
464.h264ref              11.19%
471.omnetpp            11.80%
473.astar                  -0.29%
483.xalancbmk         8.87%
Score                       8.12%

These are good numbers and show that ILP32 has performance advantage over LP64.

SPEC CPU2006 is a user-land benchmark and spends almost no time in the kernel (by design).  Similar results for a kernel-focused benchmark would be highly interesting too, and kernel reviewers have asked for these a couple of times.  Do you plan to run kernel benchmarks on the hardware you have?

Thanks,

--
Maxim Kuvyrkov
www.linaro.org