Messages in this thread | | | Subject | Re: [PATCH] perf/x86: check ucode before disabling PEBS on SandyBridge | From | Peter Zijlstra <> | Date | Tue, 12 Jun 2012 19:13:23 +0200 |
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On Tue, 2012-06-12 at 19:09 +0200, Stephane Eranian wrote: > > Instead of registering a microcode notifier, why not checking the > > availability of pebs dynamically with each syscall in > > intel_pmu_hw_config()? It looks like intel_snb_verify_ucode() is not > > that much expensive. We can perform the check only if the event > could > > be for pebs and if pebs is broken. The check could be repeated when > > setting up a new event after ucode could potentially has been > updated > > (e.g. after bringing a cpu online or so).
Because you then end up with a for_each_online_cpu() loop in there, that's not pretty and quite horrible on large systems when you need to create nr_cpus events.
Furthermore, ucode update is the rare thing, creating events happens much more frequently.
> That's what I had in my original version.
Right, but you really need to check all cpus, not just the one you happen to run on or the boot cpu.
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