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Message-Id: <1224880083.7753.6.camel@twins> Date: Fri, 24 Oct 2008 22:28:03 +0200 From: Peter Zijlstra <a.p.zijlstra@...llo.nl> To: Chris Friesen <cfriesen@...tel.com> Cc: linux-kernel@...r.kernel.org, mingo@...e.hu, efault@....de, vatsa@...ibm.com Subject: Re: [PATCH 7/8] sched: non-zero lag renice On Fri, 2008-10-24 at 11:47 -0600, Chris Friesen wrote: > Peter Zijlstra wrote: > > > Then renicing, esp when lowering nice value (getting heavier), its possible > > to get into a starvation scenario. If you got too much runtime as a very > > light task, you get shot way far too the right, which means you'll have to > > wait for a long time in order to run again. > > > > If during that wait you get reniced down, fairness would suggest you get run > > earlier, because you deserve more time. > > > > This can be solved by scaling the vruntime so that we keep the real-time > > lag invariant. > > If we've already been shot way out to the right, presumably that would give us > a large real-time lag. If we renice to a lower nice level, wouldn't we want > to reduce the real-time lag rather than make it constant? Ah, see but a 1ms real-time lag might be gigantic on weight=15, but nearly nothing on weight=88761. 1e6 * 1024/15 is massively larger than 1e6 * 1024/88761. 1000000*1024/15 = 68266666 1000000*1024/88761 = 11536 -- 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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