stall-free memory reads ? (possibly stale) ?

[Luigi Rizzo]

thank you, much appreciated.

On Fri, Apr 8, 2016 at 11:22 PM, Slawa Olhovchenkov <slw at zxy.spb.ru> wrote:

> On Fri, Apr 08, 2016 at 06:24:16PM +0200, Luigi Rizzo wrote:
>
> > Hi,
> > I have an application with two threads sharing a memory variable,
> > one continuously writing, one continuously reading.
> >
> > Because of the way my system works, the reader can tolerate reading
> > stale data, but it should not stall on memory reads (the line
> > is on the local cache for the reader, just might be invalidated).
> >
> > I was wondering if there is some way (either generic or
> > x86-specific, either simple or convoluted, possibly using
> > multiple versions of the shared variable in different cache
> > lines) to make sure that reads never stalls (or, equivalently,
> > let me read stale values from the cache) ?
> >
> > I have done some experiments and on a single-socket machines
> > the stallled reads take some 50ns; on a dual socket machine
> > the stall penalty grows to about 200ns.
>
> Can this link help to you?
>
> https://tu-dresden.de/die_tu_dresden/zentrale_einrichtungen/zih/forschung/projekte/benchit/2015_ICPP_authors_version.pdf
>
>


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