Re: [PATCH RESEND v4] sched/fair: Add advisory flag for borrowing a timeslice

* Khalid Aziz [off-list ref] wrote:

On 12/19/2014 04:57 PM, Thomas Gleixner wrote:

quoted

On Fri, 19 Dec 2014, Khalid Aziz wrote:

quoted

The queuing problem caused by a task taking a contended lock just before its
current timeslice is up which userspace app wouldn't know about, is a real
problem nevertheless.

We know that already.

quoted

My patch attempts to avoid the contention in the first
place. futex with adaptive spinning is a post-contention solution that tries
to minimize the cost of contention but does nothing to avoid the contention.

I never said that adaptive spinning can solve that problem.

If you would have carefuly read what I wrote, you might have noticed,
that I said:

     a proper futex like spin mechanism

Can you spot the subtle difference between that phrase and 'futex with
adaptive spinning'?

quoted

Solving this problem using futex can help only if the userspace lock uses
futex.

A really fundamentally new and earth shattering insight.

If you would spend your time to actually digest what maintainers are
telling you, we might make progress on that matter.

But you prefer to spend your time by repeating yourself and providing
completely useless information.

What you are missing completely here is that neither me nor other
maintainers involved care about how you spend your time. But we very
much care about the time WE waste with your behaviour.

I am sorry that you feel the need to continue to resort to 
personal attacks [...]

Thomas did not attack your person AFAICS - he criticised your 
arguments with increasing volume, because he did not see you 
respond to his arguments in substance.

even after I made it clear in my last response that I was not 
going to pursue this patch. There is no possibility of a 
productive discussion of a solution at this point. [...]

I think there is very much a possibility of a productive 
discussion:

[...] I hope someone else can find a solution you find 
acceptable.

to implement what Thomas suggested in the discussion: a proper 
futex like spin mechanism? That looks like a totally acceptable 
solution to me, without the disadvantages of your proposed 
solution.

Thanks,

	Ingo