当我在boost::iostreams::mapped_file_source打开电话时，我的程序会挂起大约两分钟。我尝试在此时将gdb附加到进程，并且回溯显示
(gdb) backtrace
#0 0x00007f779226687a in mmap64 () at ../sysdeps/unix/syscall-template.S:81
#1 0x00007f7793c60f58 in boost::iostreams::detail::mapped_file_impl::try_map_file(boost::iostreams::basic_mapped_file_params<boost::iostreams::detail::path>) () from /usr/lib/x86_64-linux-gnu/libboost_iostreams.so.1.54.0
#2 0x00007f7793c61028 in boost::iostreams::detail::mapped_file_impl::map_file(boost::iostreams::basic_mapped_file_params<boost::iostreams::detail::path>&) () from /usr/lib/x86_64-linux-gnu/libboost_iostreams.so.1.54.0
#3 0x00007f7793c614d2 in boost::iostreams::detail::mapped_file_impl::open(boost::iostreams::basic_mapped_file_params<boost::iostreams::detail::path>) () from /usr/lib/x86_64-linux-gnu/libboost_iostreams.so.1.54.0
#4 0x00007f7793c6168e in boost::iostreams::mapped_file_source::open_impl(boost::iostreams::basic_mapped_file_params<boost::iostreams::detail::path> const&) () from /usr/lib/x86_64-linux-gnu/libboost_iostreams.so.1.54.0
#5 0x0000000000e07f86 in boost::iostreams::mapped_file_source::open<boost::iostreams::detail::path> (this=this@entry=0x1db63f8, p=...) at /usr/include/boost/iostreams/device/mapped_file.hpp:406
#6 0x0000000000e08011 in boost::iostreams::mapped_file_source::open<boost::filesystem::path> (this=this@entry=0x1db63f8, path=..., length=length@entry=18446744073709551615, offset=offset@entry=0)
at /usr/include/boost/iostreams/device/mapped_file.hpp:416
为什么打开电话这么慢？难道不能快速回到这里吗？