From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ingo Molnar Subject: Re: [PATCH RESEND v4] sched/fair: Add advisory flag for borrowing a timeslice Date: Tue, 23 Dec 2014 11:52:51 +0100 Message-ID: <20141223105251.GB22203@gmail.com> References: <1418928259-6311-1-git-send-email-khalid.aziz@oracle.com> <20141218222846.GH30905@twins.programming.kicks-ass.net> <54935842.5020507@oracle.com> <54936562.5070502@oracle.com> <54949BF0.8030403@oracle.com> <5498498B.90703@oracle.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <5498498B.90703-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org> Sender: linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Khalid Aziz Cc: Thomas Gleixner , Peter Zijlstra , corbet-T1hC0tSOHrs@public.gmane.org, mingo-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, hpa-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org, riel-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org, rientjes-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org, ak-VuQAYsv1563Yd54FQh9/CA@public.gmane.org, mgorman-l3A5Bk7waGM@public.gmane.org, raistlin-k2GhghHVRtY@public.gmane.org, kirill.shutemov-VuQAYsv1563Yd54FQh9/CA@public.gmane.org, atomlin-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, avagin-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org, gorcunov-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org, serge.hallyn-Z7WLFzj8eWMS+FvcfC7Uqw@public.gmane.org, athorlton-sJ/iWh9BUns@public.gmane.org, oleg-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, vdavydov-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org, daeseok.youn-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, keescook-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org, yangds.fnst-BthXqXjhjHXQFUHtdCDX3A@public.gmane.org, sbauer-F61uvSdQLzf2fBVCVOL8/A@public.gmane.org, vishnu.ps-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org, axboe-b10kYP2dOMg@public.gmane.org, paulmck-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-doc-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-api@vger.kernel.org * Khalid Aziz wrote: > On 12/19/2014 04:57 PM, Thomas Gleixner wrote: > >On Fri, 19 Dec 2014, Khalid Aziz wrote: > >>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. > > > >>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'? > > > >>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