| Date | Thu, 5 Jun 2014 15:16:47 +0200 | Subject | Re: [PATCH 9/9] perf/x86: add syfs entry to disable HT bug workaround | From | Stephane Eranian <> |
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On Thu, Jun 5, 2014 at 2:59 PM, Peter Zijlstra <peterz@infradead.org> wrote: > On Thu, Jun 05, 2014 at 02:55:05PM +0200, Stephane Eranian wrote: >> On Thu, Jun 5, 2014 at 2:50 PM, Peter Zijlstra <peterz@infradead.org> wrote: >> > On Thu, Jun 05, 2014 at 12:16:01PM +0100, Matt Fleming wrote: >> >> On 5 June 2014 11:19, Stephane Eranian <eranian@google.com> wrote: >> >> > How would you know that you have a uniform workload from inside >> >> > the kernel? >> >> >> >> That's what I'm asking you ;-) >> >> >> >> >> Does cpu_sibling_map not give you some indication of whether HT is >> >> >> enabled? I think the topology_thread_cpumask() is the topology API for >> >> >> that. But I could most definitely be wrong. Hopefully someone on the >> >> >> Cc list will know. >> >> >> >> >> > Remember trying some of that, but when perf_event is initialized, those >> >> > masks are not yet setup properly. >> >> >> >> Oh, bummer. >> > >> > So we init perf very early to get nmi-watchdog up and running, but >> > there's no reason you cannot register a second initcall later and flip >> > the switch from it there. >> >> and what initcall would that be? > > Pretty much anything !early_initcall() is ran after SMP bringup iirc.
Ok, we can try this. Need to check the impact on NMI watchdog if already active.
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