Messages in this thread | | | Date | Fri, 17 Feb 2006 13:51:46 +1100 | From | Peter Williams <> | Subject | Re: [PATCH] Fix smpnice high priority task hopping problem |
| |
Peter Williams wrote: > Siddha, Suresh B wrote: > >> Andrew, Please don't apply this patch. This breaks the existing HT >> (and multi-core) scheduler optimizations. >> >> Peter, on a DP system with HT, if we have only two runnable processes >> and they end up running on the two threads of the same package, with >> your patch, migration thread will never move one of those processes to >> the idle package.. > > > On a normal system, would either of them be moved anyway? > >> >> To fix my reported problem, we need to make sure that >> find_busiest_group() >> doesn't find an imbalance.. > > > I disagree. If this causes a problem with your "optimizations" then I > think that you need to fix the "optimizations". > > There's a rational argument (IMHO) that this patch should be applied > even in the absence of the smpnice patches as it prevents > active_load_balance() doing unnecessary work. If this isn't good for > hypo threading then hypo threading is a special case and needs to handle > it as such.
OK. The good news is that (my testing shows that) the "sched: fix smpnice abnormal nice anomalies" fixes the imbalance problem and the consequent CPU hopping.
BUT I still think that this patch (modified if necessary to handle any HT special cases) should be applied. On a normal system, it will (as I've already said) stop active_load_balance() from doing a lot of unnecessary work INCLUDING holding the run queue locks for TWO run queues for no good reason.
Peter -- Peter Williams pwil3058@bigpond.net.au
"Learning, n. The kind of ignorance distinguishing the studious." -- Ambrose Bierce - 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/
| |