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SubjectRe: [PATCH tip/tracing/markers] new probes manager

* Mathieu Desnoyers <compudj@krystal.dyndns.org> wrote:

> * Mathieu Desnoyers (mathieu.desnoyers@polymtl.ca) wrote:
> > * Lai Jiangshan (laijs@cn.fujitsu.com) wrote:
> > >
> > > this patch use a new probes manager for marker.
> > >
> > > the most important benefit of this patch is:
> > > 1) smp_rmb() is removed from the critical path. as we know rmb()
> > > is very expensive.
> > >
> >
> > Do you have performance measurements for this ? On x86 it's a nop,
> > AFAIK.
>
> My statement above is inexact : x86_64 uses lfence for rmb(). But
> numbers would still be welcome.

yes, the statement that rmb() is very expensive looks dubious. It is
absolutely cheap everywhere.

Ingo


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