Date: Fri, 27 Oct 2006 21:36:27 -0400 From: "Alexandre \"Sunny\" Kovalenko" <Alex.Kovalenko@verizon.net> To: Julian Elischer <julian@elischer.org> Cc: Daniel Eischen <deischen@freebsd.org>, Paul Allen <nospam@ugcs.caltech.edu>, current@freebsd.org Subject: Re: Comments on the KSE option Message-ID: <1161999387.872.29.camel@RabbitsDen.RabbitsLawn.verizon.net> In-Reply-To: <4542B171.8050601@elischer.org> References: <45425D92.8060205@elischer.org> <20061027201838.GH30707@riyal.ugcs.caltech.edu> <Pine.GSO.4.64.0610271634160.7105@sea.ntplx.net> <1161998104.872.18.camel@RabbitsDen.RabbitsLawn.verizon.net> <4542B171.8050601@elischer.org>
next in thread | previous in thread | raw e-mail | index | archive | help
On Fri, 2006-10-27 at 18:25 -0700, Julian Elischer wrote: > Alexandre "Sunny" Kovalenko wrote: > > On Fri, 2006-10-27 at 16:41 -0400, Daniel Eischen wrote: > >> On Fri, 27 Oct 2006, Paul Allen wrote: > >> > >>>> From Julian Elischer <julian@elischer.org>, Fri, Oct 27, 2006 at 12:27:14PM -0700: > >>>> The aim of the fair scheduling code is to ensure that if you, as a user, > >>>> make a process that starts 1000 threads, and I as a user, make an > >>>> unthreaded process, then I can still get to the CPU at somewhat similar > >>>> rates to you. A naive scheduler would give you 1000 cpu slots and me 1. > >>> Ah. Let me be one of the first to take a crack at attacking this idea as > >>> a mistake. > >> No, it is POSIX. You, the application, can write a program with > >> system scope or process scope threads and get whatever you behavior > >> you want, within rlimits of course. > >> > >> If you want unfair scheduling, then create your threads with > >> system scope contention, otherwise use process scope. The > >> kernel should be designed to allow both, and have adjustable > >> limits in place for (at least) system scope threads. > >> > >> Noone is saying that you can't have as many system scope threads > >> as you want (and as allowed by limits), just that you must also > >> be able to have process scope threads (with probably higher limits > >> or possibly no limits). > >> > > I might be missing something here, but OP was separating M:N (which is > > what you are referring to above), and "fairness" (not giving process > > with 1000 *system scope* threads 1000 CPU scheduling slots). As far as I > > know the first one is POSIX and the second one is not. > > > > FWIW: as an application programmer who spent considerable amount of time > > lately trying to make heavily multithreaded application run most > > efficiently on 32-way machine, I would rather not have to deal with > > "fairness" -- M:N is bad enough. > > > > > no, fairness is making sure that 1000 process scope threads > do not negatively impact other processes. > 1000 system scope threads are controlled by your ulimit settings > (Each one counts as a process.) > > I apologize for misinterpreting your words. But then, if I have M:N set to 10:1, I would expect application with 1000 process scope threads to have as many CPU slots as 100 processes, or, if I have 10 system scope threads and 990 process scope threads, I would expect application to have as many CPU slots as 109 processes. Is this what you refer to as "fairness"? -- Alexandre "Sunny" Kovalenko
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?1161999387.872.29.camel>