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Date: Sat, 9 Apr 2016 00:22:37 +0300
From: Slawa Olhovchenkov <slw@zxy.spb.ru>
To: Luigi Rizzo <rizzo@iet.unipi.it>
Cc: freebsd-current@freebsd.org
Subject: Re: stall-free memory reads ? (possibly stale) ?
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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