[Bug gcov-profile/89307] -fprofile-generate binary may be too slow in multithreaded environment due to cache-line conflicts on counters

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89307

--- Comment #7 from Richard Biener <rguenth at gcc dot gnu.org> ---
Btw, use of TLS has

 * size of counters overhead (one could use char sized TLS counters and
   update the global ones with locking on overflow)
 * tear-down/build-up cost at thread termination/creation

the advantage is of course it's simple implementation-wise.