Messages in this thread | | | Date | Mon, 7 Jan 2019 17:32:27 +0100 | From | Peter Zijlstra <> | Subject | Re: [RFC v2 0/6] x86: dynamic indirect branch promotion |
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On Thu, Jan 03, 2019 at 02:18:15PM -0800, Andi Kleen wrote: > Nadav Amit <namit@vmware.com> writes: > > > > - Do we use periodic learning or not? Josh suggested to reconfigure the > > branches whenever a new target is found. However, I do not know at > > this time how to do learning efficiently, without making learning much > > more expensive. > > FWIW frequent patching will likely completely break perf Processor Trace > decoding, which needs a somewhat stable kernel text image to decode the > traces generated by the CPU. Right now it relies on kcore dumped after > the trace usually being stable because jumplabel changes happen only > infrequently. But if you start patching frequently this assumption will > break. > > You would either need a way to turn this off, or provide > updates for every change to the trace, so that the decoder can > keep track.
I'm thining it would be entirely possible to create and feed text_poke events into the regular (!aux) buffer which can be timestamp correlated to the PT data.
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