From: Grant Grundler <grundler@dsl2.external.hp.com>
To: "John David Anglin" <dave@hiauly1.hia.nrc.ca>
Cc: parisc-linux@lists.parisc-linux.org
Subject: Re: [parisc-linux] Branch Prediction
Date: Sat, 26 Oct 2002 19:23:03 -0600 [thread overview]
Message-ID: <20021027012303.7B576484E@dsl2.external.hp.com> (raw)
In-Reply-To: Message from "John David Anglin" <dave@hiauly1.hia.nrc.ca> of "Sat, 26 Oct 2002 13:05:04 EDT." <200210261705.g9QH54Zx002355@hiauly1.hia.nrc.ca>
"John David Anglin" wrote:
> I wonder if the PA-8700 in the rp2470 has it?
gsyprf11 is a 650Mhz PA8700. please try it.
> I suppose it also could be an add-on chip.
Think so?
After reading the description I had the impression BTS has to be on chip
and integrated in order to get the speed. But I'm just a SW engineer...
> I am guessing but I think setting it would help on machines with
> dynamic prediction hardware. There is probably a paper somewhere
> on this on the HP site.
> My understanding is that pc-relative branches can be predicted
> from examination of the code. Indirect branches (e.g., call
> returns) can't.
yes. IIRC, branches forward tend to not be taken and branches backwards
tend to be loops. Or something along that line. But with PBO, the
static hints are better. And HPUX has a very cool "driver" called
"flipper" that will flip to static hints to match performance path
at run time.
> I don't know how the dynamic prediction hardware
> works but I would think it wouldn't be there if it didn't
> improve branch prediction.
yeah - I'll what I can learn about it this week.
thanks,
grant
next prev parent reply other threads:[~2002-10-27 1:23 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-10-25 17:17 [parisc-linux] Branch Prediction John David Anglin
2002-10-26 5:11 ` Grant Grundler
2002-10-26 17:05 ` John David Anglin
2002-10-27 1:23 ` Grant Grundler [this message]
2002-10-27 10:20 ` N.Leymann
2002-11-01 21:30 ` John David Anglin
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