Re: PostgreSQLv14 TPC-H performance GCC vs Clang

> .. optimisation flags like O3
> And please suggest ... to check on the performance difference

The Phoronix has been tested the PostgreSQL 13 with Clang 12 + GCC 11.1 On
Xeon Ice Lake
* "The CFLAGS/CXXFLAGS set throughout testing were "-O3 -march=native
-flto" *
* as would be common for HPC systems when building performance sensitive
code."*
*and the results:*

https://www.phoronix.com/scan.php?page=article&item=clang12-gcc11-icelake&num=4
( see ~ bottom of the page )
only the Postgres ( GCC 11 vs. LLVM Clang 12 Benchmarks On Xeon Ice Lake )

https://openbenchmarking.org/result/2105299-IB-COMPILERT91&sgm=1&ppt=D&sor&sgm=1&ppt=D&oss=Postgresql
maybe you can replicate the Phoronix results ( but this is only gcc11.1
! )
"Compare your own system(s) to this result file with the Phoronix Test
Suite
by running the command: phoronix-test-suite benchmark
2105299-IB-COMPILERT91"

Regards.
Imre

arjun shetty <arjunshetty955(at)gmail(dot)com> ezt írta (időpont: 2021. nov. 2.,
K, 18:13):

> Hi
> PostgreSQLv14 source code build with GCCv11.2 and Clangv12(without JIT)
> with optimisation flags like O3 and tested with HammerDB
> Observed TPC-H , GCC performance better than Clang(without JIT). The
> performance difference ~22% and also noticed the assembly code difference
> GCC vs Clang( e.g. GCC inlined functionality compared to Clang).
>
> Environment details:
> ————————-
> OS :RHEL8.4
> Bare metal : Apple/AMD EPYC/IBM
> Test(TPC-H) Benchmark Environment:HammerDB
>
> Is the performance difference mainly because of below points ?
> 1 data over flow and calculations like int128(int128.c) and C arithmetic
> operations(functions include in float.h e.g float4_mul)
>
> And please suggest is any another functionality or code points need to
> check on the performance difference
>