Re: [RFCv2] Dynamic lock elision support

["Carlos O'Donell" <carlos at redhat dot com>]

On 08/31/2015 03:24 PM, Paul E. Murphy wrote:
> Narrowing my focus here, we should have a runtime
> mechanism to disable elision for those applications
> which experience significant degradation from the
> non-optional nature of this feature.
> 
> I think we can table the discussion of runtime
> tunable parameters as it is highly dependent on the
> framework which emerges.
> 
> In the meantime, there is a need to turn this
> off for select workloads. It would be preferable
> to add this in such a way that it can be easily
> merged into the tunables framework when it
> does evolve.

Is this theoretical or do you have such customer workloads,
I'm not talking about the synthetic benchmarks you have, where
default pthread mutexes cause the application to experience
significant performance loss?

If you are proposing that your patch is sufficiently important
to bypass the tunables discussion and get accepted right away
then you need to give sufficient detail for the community to
accept that we need to move quickly because users are having
problems.

Otherwise I think that Siddhesh's present work should get
reviewed by you, and others, get merged, and represent the
basis for an internal tunables API that enables per-env-var
tunables.

In summary, we can add "yet one more env var" for you, but
you have to justify it.

Cheers,
Carlos.