Messages in this thread | | | Date | Mon, 27 Oct 2008 19:26:55 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH tip/tracing/markers] new probes manager |
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* 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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