On Fri, Mar 27, 2015 at 03:26:17PM -0400, Eric van Gyzen wrote: > In a nutshell:
> Clang emits SSE instructions on amd64 in the common path of > pthread_mutex_unlock. This reduces performance by a non-trivial > amount. I'd like to disable SSE in libthr. How about saving and restoring the FPU/SSE state eagerly instead of the current CR0.TS-based lazy method? There is overhead associated with #NM exception handling (fpudna) which is not worth it if FPU/SSE are used often. This would apply to userland threads only; kernel threads normally do not use FPU/SSE and handle the FPU/SSE state manually if they do. There is performance improvement potential in using SSE for optimizing string functions, for example. Even a simple SSE2 strlen easily outperforms the already optimized lib/libc/string/strlen.c in a microbenchmark, and many other string functions are slow byte-at-a-time implementations. -- Jilles Tjoelker _______________________________________________ freebsd-current@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-current To unsubscribe, send any mail to "freebsd-current-unsubscr...@freebsd.org"
