> GCC vs Clang related: As I see - with LLVM/Clang 14.0 ( X86_64 -O3 ) ~12% performance increase expected with the new optimisation ( probably adapted from gcc ) - https://twitter.com/djtodoro/status/1466808507240386560 - https://www.phoronix.com/scan.php?page=news_item&px=LLVM-Clang-14-Hoist-Load
regards, Imre arjun shetty <arjunshetty...@gmail.com> ezt írta (időpont: 2021. nov. 16., K, 11:10): > Yes, currently focusing affects queries as well. > In meanwhile on analysis(hardware level) and sample examples noticed > 1. GCC performance better than Clang on int128 . > 2. Clang performance better than GCC on long long > the reference example > https://stackoverflow.com/questions/63029428/why-is-int128-t-faster-than-long-long-on-x86-64-gcc > > 3.GCC enabled with “ fexcess-precision=standard” (precision cast for > floating point ). > > Is these 3 points can make performance difference GCC vs Clang in > PostgreSQLv14 in Apple/AMD/()environment(intel environment need to check). > In these environment int128 enabled wrt PostgreSQLv14. > > On Friday, November 5, 2021, Tomas Vondra <tomas.von...@enterprisedb.com> > wrote: > >> Hi, >> >> IMO this thread provides so little information it's almost impossible to >> answer the question. There's almost no information about the hardware, >> scale of the test, configuration of the Postgres instance, the exact build >> flags, differences in generated asm code, etc. >> >> I find it hard to believe merely switching from clang to gcc yields 22% >> speedup - that's way higher than any differences we've seen in the past. >> >> In my experience, the speedup is unlikely to be "across the board". There >> will be a handful of affected queries, while most remaining queries will be >> about the same. In that case you need to focus on those queries, see if the >> plans are the same, do some profiling, etc. >> >> >> regards >> >> -- >> Tomas Vondra >> EnterpriseDB: http://www.enterprisedb.com >> The Enterprise PostgreSQL Company >> >
