On Wednesday 23 March 2005 18:09, Bodo Stroesser wrote: > [EMAIL PROTECTED] wrote: > > Use rep_nop instead of barrier for cpu_relax, following $(SUBARCH)'s > > doing that (i.e. i386 and x86_64). > > IIRC, Jeff had the idea, to use sched_yield() for this (from a discussion > on #uml). Hmm, makes sense, but this is to benchmark well... I remember from early discussions on 2.6 scheduler that using sched_yield might decrease performance (IIRC starve the calling application).
Also, that call should be put inside the idle loop, not for cpu_relax, which is very different, since it is used (for instance) in kernel/spinlock.c for spinlocks, and in such things. The "Pause" opcode is explicitly recommended (by Intel manuals, I don't recall why) for things like spinlock loops, and using yield there would be bad. > S390 does something similar using a special DIAG-opcode that > gives permission to zVM, that another Guest might run. > On a host running many UMLs, this might improve performance. > > So, I would like to have the small patch below (it's not tested, just an > idea). -- Paolo Giarrusso, aka Blaisorblade Linux registered user n. 292729 http://www.user-mode-linux.org/~blaisorblade - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
