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Date: Thu, 21 Feb 2013 09:35:50 +0800 From: Alex Shi <alex.shi@...el.com> To: Peter Zijlstra <peterz@...radead.org> CC: torvalds@...ux-foundation.org, mingo@...hat.com, tglx@...utronix.de, akpm@...ux-foundation.org, arjan@...ux.intel.com, bp@...en8.de, pjt@...gle.com, namhyung@...nel.org, efault@....de, vincent.guittot@...aro.org, gregkh@...uxfoundation.org, preeti@...ux.vnet.ibm.com, viresh.kumar@...aro.org, linux-kernel@...r.kernel.org, morten.rasmussen@....com Subject: Re: [patch v5 06/15] sched: log the cpu utilization at rq On 02/20/2013 11:20 PM, Peter Zijlstra wrote: > On Wed, 2013-02-20 at 22:33 +0800, Alex Shi wrote: >>> There's generally a better value than 100 when using computers.. >> seeing >>> how 100 is 64+32+4. >> >> I didn't find a good example for this. and no idea of your suggestion, >> would you like to explain a bit more? > > Basically what you're doing ends up being fixed point math, using 100 as > unit is inefficient, pick a power-of-2 and everything reduces to > bit-shifts. > > http://en.wikipedia.org/wiki/Fixed-point_arithmetic > > So use 128 or 1024 or whatever and you don't need mult and div > instructions to represent [0,1] > got it. will reconsider this. -- Thanks Alex -- 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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