Re: [PATCH] Fix smpnice high priority task hopping problem

Peter Williams
2006-02-17T03:16:17Z

Siddha, Suresh B wrote:
> On Fri, Feb 17, 2006 at 01:51:46PM +1100, Peter Williams wrote:
>
>>Peter Williams wrote:
>>
>>>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.
>
>
> Thats because find_busiest_group() is no longer showing the imbalance :)
> Anyhow if I get time I will review this patch before I start my vacation.
> Otherwise I assume Nick and Ingo will review this closely..
>
>
>>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.
>
>
> Please see my earlier response to this..

I saw nothing there to convince me that this patch isn't worthwhile.
Perhaps a better explanation would help me?