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Date: Tue, 12 May 2009 07:57:39 +0200 From: Peter Zijlstra <peterz@...radead.org> To: Jussi Laako <jussi@...arnerd.net> Cc: James Courtier-Dutton <James@...erbug.co.uk>, linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>, d.faggioli@...up.it Subject: Re: [RFC][PATCH] Multimedia scheduling class, take 2 On Mon, 2009-05-11 at 11:22 +0300, Jussi Laako wrote: > Hi, > > Peter Zijlstra wrote: > > Right, and I think the solution to this problem is twofold, 1) > > application writers should start writing (soft) realtime applications if > > they want (soft) realtime behaviour -- there's just no way around that. > > Just to avoid need for reviewing and reworking ~800 klocs of user space > code in just gstreamer, here's a second take on patches. This time > splitting things into smaller pieces. Attached patch exposes 40 > priorities ~ nice values as something accessible through > sched_()/pthreads API in order to control priorities of individual > threads. Current Linux implementation of SCHED_OTHER is broken in a way, > that it exposes only one single priority level - 0. Thus no possibility > to properly control priorities of threads through pthread API. This is > patch is against 2.6.29.2 and not tested, but builds. I can also send > rest of the changes as separate small feature patches as needed. > However, before doing any more work I would like to hear opinions on > this and especially what is wrong with the code or idea... > > > And 2), the kernel can help by providing a deadline based scheduler, > > which should make the above easier and less likely to mess up the rest > > of the system. ie. a deadline scheduled application will not exceed its > > allotted budget, unlike a FIFO scheduled app. > > Any news on this one? Utter lack of time on my side to work on any of the problems there. As to the patch, I still think its an exceedingly bad idea to create such a horridly ill defined scheduler class. There's nothing that keeps people from stuffing everything in there and either generating DoS issues or still generating bad interactivity. I certainly don't think the current situation is bad enough to warrant things like that, media on my machines works peachy (*cheer* for XV on R600). I happen to know that Dario (CC'ed) has been working on a userspace framework to ease the use of writing soft-realtime (soft as in media based applications) in C, mitigating a lot of the risks of using SCHED_FIFO and the like. Perhaps he's willing to expand on that. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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