Messages in this thread | | | Date | Sat, 18 Mar 2006 00:46:07 +1100 | From | Nick Piggin <> | Subject | Re: [PATCH] sched: activate SCHED BATCH expired |
| |
Con Kolivas wrote: > On Saturday 18 March 2006 00:26, Nick Piggin wrote: > >>Con Kolivas wrote: >> >>>-static inline void __activate_task(task_t *p, runqueue_t *rq) >>>+static void __activate_task(task_t *p, runqueue_t *rq) >>> { >>>- enqueue_task(p, rq->active); >>>+ if (batch_task(p)) >>>+ enqueue_task(p, rq->expired); >>>+ else >>>+ enqueue_task(p, rq->active); >>> inc_nr_running(p, rq); >>> } >> >>I prefer: >> >> prio_array_t *target = rq->active; >> if (batch_task(p)) >> target = rq->expired; >> enqueue_task(p, target); >> >>Because gcc can use things like predicated instructions for it. >>But perhaps it is smart enough these days to recognise this? >>At least in the past I have seen it start using cmov after doing >>such a conversion. >> >>At any rate, I think it looks nicer as well. IMO, of course. > > > Well on my one boring architecture here is a before and after, gcc 4.1.0 with > optimise for size kernel config:
> I'm not attached to the style, just the feature. If you think it's warranted > I'll change it. >
I guess it isn't doing the cmov because it doesn't want to do the extra load in the common case, which is fair enough (are you compiling for a pentiumpro+, without generic x86 support? what about if you turn off optimise for size?)
At least other archtectures might be able to make better use of it, and I agree even for i386 the code looks better (and slightly smaller).
-- SUSE Labs, Novell Inc. Send instant messages to your online friends http://au.messenger.yahoo.com
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |