Messages in this thread | | | Date | Tue, 27 Jan 2015 17:28:15 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH 5/5] sched/rt: Optimize find_lowest_rq() to select a cache hot cpu |
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On Tue, Jan 27, 2015 at 09:56:26AM -0500, Steven Rostedt wrote: > On Tue, 27 Jan 2015 15:21:36 +0100 > Peter Zijlstra <peterz@infradead.org> wrote: > > > On Mon, Jan 19, 2015 at 04:49:40AM +0000, Xunlei Pang wrote: > > > In find_lowest_rq(), if we can't find a wake_affine cpu from > > > sched_domain, then we can actually determine a cache hot cpu > > > instead of simply calling "cpumask_any(lowest_mask)" which > > > always returns the first cpu in the mask. > > > > > > So, we can determine the cache hot cpu during the interation of > > > sched_domain() in passing. > > > > Steve, I'm not getting this. Why are we using WAKE_AFFINE here? > > > > It originated from Gregory Haskins topology patches. See > 6e1254d2c41215da27025add8900ed187bca121d
Indeed so; it seems an arbitrary choice.
And the proposed patch seems like a convoluted way to simply remove the ->flags & SD_WAKE_AFFINE test.
Of course, the entire domain loop there assumes a lower domain is better; yay for SMT being such a good counter example ;-)
Of course, if we remove it here; we should do too for deadline.
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