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Date: Mon, 24 Sep 2007 13:08:51 +0200 From: Peter Zijlstra <a.p.zijlstra@...llo.nl> To: Mike Galbraith <efault@....de> Cc: Tong Li <tong.n.li@...el.com>, Ingo Molnar <mingo@...e.hu>, dimm <dmitry.adamushko@...il.com>, linux-kernel@...r.kernel.org, Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com> Subject: Re: [git] CFS-devel, group scheduler, fixes On Mon, 24 Sep 2007 12:42:15 +0200 Mike Galbraith <efault@....de> wrote: > On Mon, 2007-09-24 at 12:24 +0200, Peter Zijlstra wrote: > > > how about something like: > > > > s64 delta = (s64)(vruntime - min_vruntime); > > if (delta > 0) > > min_vruntime += delta; > > > > That would rid us of most of the funny conditionals there. > > That still left me with negative min_vruntimes. The pinned hogs didn't > lock my box up, but I quickly got the below, so hastily killed it. > > se.wait_max : 7.846949 > se.wait_max : 301.951601 > se.wait_max : 7.071359 > Odd, the idea (which I think is clear) is that min_vruntime can wrap around the u64 spectrum. And by using min_vruntime as offset to base the key around, we get a signed but limited range key-space. (because we update min_vruntime to be the leftmost task (in a monotonic fashion)) So I'm having trouble with these patches, that is, both your wrap around condition of: if (likely(new_rq->cfs.min_vruntime)) as well as the last patchlet: if (((s64)vruntime > (s64)min_vruntime) || in that neither of these changes make sense in what its trying to do. Its perfectly valid for min_vruntime to exist in 1ULL << 63. - 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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