Messages in this thread | | | Date | Mon, 19 Oct 2015 09:08:12 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH 1/4] x86, perf: Use a new PMU ack sequence on Skylake |
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* Peter Zijlstra <peterz@infradead.org> wrote:
> On Fri, Oct 16, 2015 at 06:35:14AM -0700, Andi Kleen wrote: > > > > In principle the sequence should work on other CPUs too, but > > > > since I only tested on Skylake it is only enabled there. > > > > > > I would very much like a reduction of the ack states. You introduced the > > > late thing, which should also work for everyone, and now you introduce yet > > > another variant. > > > > Ingo suggested to do it this way. Originally I thought it wasn't needed, but I > > think now that late-ack made some of the races that eventually caused Skylake > > LBR to fall over worse. So in hindsight it was a good idea to not use it > > everywhere. > > > > > I would very much prefer a single ack scheme if at all possible. > > > > Could enable it everywhere, but then users would need to test it on most types > > of CPUs, as I can't. > > I think Mike still has a Core2 machine (and I might be able to dig out a > laptop), Ingo should have a NHM(-EP), I have SNB, IVB-EP, HSW. So if you could > test at least BDW and SKL we might have decent test coverage. > > Ingo, do you want to first merge the safe patch and then clean up?
Yeah, would be nice to structure it that way, out of general paranoia.
Thanks,
Ingo
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