_dl_lookup_symbol_x是什么?——c++分析

I'm using valgrind/callgrind to profile my server code for some optimization. The two most used calls that callgrind is reporting to me (using kcachegrind to view) are _dl_lookup_symbol_x and do_lookup_x. However I have no idea what either of these are and can't seem to find any documentation about them.I'm using valgrind/callgrind to profile my serv