Re: [RFC PATCH] sched: wakeup buddy
From: Michael Wang
Date: Thu Feb 28 2013 - 21:18:17 EST
On 02/28/2013 05:18 PM, Mike Galbraith wrote:
> On Thu, 2013-02-28 at 16:49 +0800, Michael Wang wrote:
>> On 02/28/2013 04:24 PM, Mike Galbraith wrote:
>>> On Thu, 2013-02-28 at 16:14 +0800, Michael Wang wrote:
>>>> On 02/28/2013 04:04 PM, Mike Galbraith wrote:
>>>>> It would be nice if it _were_ a promise, but it is not, it's a hint.
>>>> Bad to know :(
>>>> Should we fix it or this is by designed? The comments after WF_SYNC
>>>> cheated me...
>>> You can't fix it, because it's not busted. You can say "Ok guys, I'm
>>> off for a nap RSN" all you want, but that won't guarantee that nobody
>>> pokes you, and hands you something more useful to do than snoozing.
>> So sync still means current is going to sleep, what you concerned is
>> this promise will be easily broken by other waker, correct?
> That makes it a lie, and it can already have been one with no help.
> Just because you wake one sync does not mean you're not going to find
> another to wake. Smart tasks are taught to look before they leap.
>> Hmm.. may be you are right, if 'perf bench sched pipe' is not the one we
>> should care, I have no reason to add this logical currently.
> Well, there is reason to identify task relationships methinks, you just
> can't rely on the fact that you're alone on the rq at the moment, and
> doing a sync wakeup to bind tasks. They _will_ lie to you :)
>> I will remove this plus branch, unless I found other benchmark could
>> benefit a lot from it.
>> Besides this, how do you think about this idea?
> I like the idea of filtering true buddy pairs, and automagically
> detecting the point when 1:N wants spreading rather a lot (fwtw). I'll
> look closer at your method, but when it comes to implementation
> opinions, the only one I trust comes out of a box in front of me.
And please let me know how it works on your box ;-)
> I'm somewhat.. "taste challenged", Peter and Ingo have some though :)
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