Re: [Gems-users] question about makePrefetch and makeRequest

["Weihang Jiang" <weihang.jiang@xxxxxxxxx>]

Thanks a lot, Luke. If I want to isolate the effect of prefetch, is it safe to just comment these two places?

On 5/30/06, Luke Yen <lyen@xxxxxxxxxxx> wrote:

Weihang:

makePrefetch() is called by Opal for store permission prefetching as
well as for prefetch instructions. It is called by both store and atomic
instructions for the former as well as prefetch instructions for the latter.

For the store permission prefetching the request is issued as soon as
the address is calculated, but the store operand is not yet ready.
Obviously its effectiveness is limited by the
latency between address calculation and store operand calculation.  Unless
you have a workload that performs a lot of stores it shouldn't make a difference
whether this feature is turned on or off.

The other prefetch case is for SPARC prefetch instructions.  Currently
we treat all prefetch instructions as loads.  In contrast, SPARC defines
other types of prefetching such as TLB entry prefetching and store
prefetching.


Luke


On Mon, 29 May 2006, Weihang Jiang wrote:

> I grepped through the opal, and found out that ruby->prefetch() is called in
>
> store_inst_t::Execute() and prefetch_inst_t::accessCache( ). It is easy to
> understand the second case, but why ruby prefetch is called in
> store_inst_t::Execute() ? Any reply is really appreciated.
>
> On 5/29/06, Weihang Jiang < weihang.jiang@xxxxxxxxx> wrote:
> >
> >  Hi,
> >     I see that opal module calls ruby module through two interfaces,
> > makePrefetch() and makeRequest(). Can anyone explain when
> > makePrefetch() should be called? How is it different from
> > makeRequest()? Any documents about it? Thanks
> >
> > Regards,
> >
> > --
> > Weihang Jiang
> >
>
>
>
> --
> Weihang Jiang
>
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-- 
Weihang Jiang