https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94268
Bug ID: 94268
Summary: std::filebuf is extremely (at least 10x) slow on
windows compared to Linux. Even much slower MSVC STL
with terrible ABI.
Product: gcc
Version: 10.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libstdc++
Assignee: unassigned at gcc dot gnu.org
Reporter: euloanty at live dot com
Target Milestone: ---
Even the hacks work the same result.
https://bitbucket.org/ejsvifq_mabmip/fast_io/src/reserver_test/benchmarks/0000.10m_size_t/unit/filebuf_io_observer.cc
D:\hg\w4\f8\fast_io\benchmarks\0000.10m_size_t\unit>g++ -o filebuf_io_observer
filebuf_io_observer.cc -Ofast -std=c++2a -s
D:\hg\w4\f8\fast_io\benchmarks\0000.10m_size_t\unit>filebuf_io_observer
output: 0.5130060000000001s
input: 0.256011s
running the same program on Linux WSL2
cqwrteur@Home-Server:~/myhome/fast_io/benchmarks/0000.10m_size_t/unit$ g++ -o
filebuf_io_observer filebuf_io_observer.cc
-Ofast -std=c++2a -s
cqwrteur@Home-Server:~/myhome/fast_io/benchmarks/0000.10m_size_t/unit$
./filebuf_io_observer
output: 0.058395978s
input: 0.06603426700000001s
It is not possible to be an optimization problem since my code has no
difference on windows and linux. I think the only reason is FILE*'s issue.
I guess the problem is just that code relies on unknown libc does not correctly
on windows. One explanation might be the underlining FILE* buffer size's
problem. I think you guys need to try larger buffer size.
Same program builds with MSVC STL (Their ABIs are terrible)
MSVC STL with hacking:
D:\hg\w4\f8\fast_io\benchmarks\0000.10m_size_t\unit>filebuf_io_observer
output: 0.119666s
input: 0.2497127s
Other comparison benchmarks
GCC 10.0.1 with msvcrt hacking.
https://bitbucket.org/ejsvifq_mabmip/fast_io/src/reserver_test/include/fast_io_legacy_impl/c/msvcrt.h
D:\hg\w4\f8\fast_io\benchmarks\0000.10m_size_t\unit>c_file_unlocked
output: 0.09216600000000001s
input: 0.12230700000000001s
GCC
