Re: [PATCH 9/9] perf/x86: add syfs entry to disable HT bug workaround

From: Stephane Eranian
Date: Thu Jun 05 2014 - 12:47:51 EST

On Thu, Jun 5, 2014 at 6:39 PM, Maria Dimakopoulou
<maria.n.dimakopoulou@xxxxxxxxx> wrote:
> On Thu, Jun 5, 2014 at 6:17 PM, Borislav Petkov <bp@xxxxxxxxx> wrote:
>> On Thu, Jun 05, 2014 at 05:45:24PM +0300, Maria Dimakopoulou wrote:
>>> The issue is that the outcoming leaked counts are not compensated
>>> by the incoming leaked counts of the sibling thread. With the workaround,
>>> corrupting events are always scheduled with an empty sibling counter.
>>> This means that their leaked counts are lost. So it is expected to see
>>> lower counts with the workaround. Note that this is not a side-effect of
>>> the workaround; leaked counts are expected to be lost with nothing
>>> measured on the sibling counter in general.
>>> In a second series we intend to re-integrate the counts for counting mode
>>> events. The workaround makes this easier because it guarantees
>>> that the sibling counter is unused, thus its counts are purely leaked
>>> counts and they can be safely re-integrated.
>> IIUC, sounds to me like reintegrating the leaked counts from the unused
>> counter should be part of the workaround too, not a second series...
> This series aims to avoid corruption of non-corrupting events.
> Re-integration of the counts is not related to this. This is why
> we chose to fix this other problem on a second series to keep
> things clean and concepts separated.
I agree with Maria here. The reintegration is different problem.
The series here helps and is a required first step. Reintegration
will be added asap.

>> --
>> Regards/Gruss,
>> Boris.
>> Sent from a fat crate under my desk. Formatting is fine.
>> --
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