On Wed, 2013-07-31 at 11:53 +0200, Peter Zijlstra wrote: > No they're quite unrelated. I think you can measure the max time we've > ever spend in newidle balance and use that to clip the values.
So I tried using the rq's max newidle balance cost to compare with the average and used sysctl_migration_cost as the initial/default max. One thing I noticed when running this on 8 socket machine was that the max idle balance cost was a lot higher during around boot time compared to after boot time. Not sure if IRQ/NMI/SMI was the cause of this. A temporary "fix" I made was to reset the max idle balance costs every 2 minutes. > Similarly, I've thought about how we updated the sd->avg_cost in the > previous patches and wondered if we should not track max_cost. > > The 'only' down-side I could come up with is that its all ran from > SoftIRQ context which means IRQ/NMI/SMI can all stretch/warp the time it > takes to actually do the idle balance. Another thing that I thought of was that max idle balance cost may also vary based on the workload that is running. So running a workload in which there are shorter idle balances after running a workload that has longer idle balances may sometimes cause it to make use of a higher idle balance cost. But I guess it is okay if we're trying to reduce overrunning the average. Jason -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
