Author: attilio Date: Sun Dec 9 04:54:22 2012 New Revision: 244046 URL: http://svnweb.freebsd.org/changeset/base/244046
Log: Add a comment on why inlining critical_enter() may not be a good idea for the general case. Reviewed by: bde MFC after: 1 week Modified: head/sys/kern/kern_switch.c Modified: head/sys/kern/kern_switch.c ============================================================================== --- head/sys/kern/kern_switch.c Sun Dec 9 04:15:51 2012 (r244045) +++ head/sys/kern/kern_switch.c Sun Dec 9 04:54:22 2012 (r244046) @@ -176,6 +176,12 @@ retry: /* * Kernel thread preemption implementation. Critical sections mark * regions of code in which preemptions are not allowed. + * + * It might seem a good idea to inline critical_enter() but, in order + * to prevent instructions reordering by the compiler, a __compiler_membar() + * would have to be used here (the same as sched_pin()). The performance + * penalty imposed by the membar could, then, produce slower code than + * the function call itself, for most cases. */ void critical_enter(void) _______________________________________________ svn-src-head@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
