linux-kernel - Re: [PATCH] x86: Align jump targets to 1 byte boundaries

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Message-ID: <20150410214421.GP28074@pd.tnic>
Date:	Fri, 10 Apr 2015 23:44:21 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Denys Vlasenko <dvlasenk@...hat.com>
Cc:	Ingo Molnar <mingo@...nel.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Jason Low <jason.low2@...com>,
	Peter Zijlstra <peterz@...radead.org>,
	Davidlohr Bueso <dave@...olabs.net>,
	Tim Chen <tim.c.chen@...ux.intel.com>,
	Aswin Chandramouleeswaran <aswin@...com>,
	LKML <linux-kernel@...r.kernel.org>,
	Andy Lutomirski <luto@...capital.net>,
	Brian Gerst <brgerst@...il.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [PATCH] x86: Align jump targets to 1 byte boundaries

On Fri, Apr 10, 2015 at 05:54:10PM +0200, Borislav Petkov wrote:
> On Fri, Apr 10, 2015 at 05:48:51PM +0200, Denys Vlasenko wrote:
> > As you know, manuals are not be-all, end-all documents.
> > They contains mistakes. And they are written before silicon
> > is finalized, and sometimes they advertise capabilities
> > which in the end had to be downscaled. It's hard to check
> > a 1000+ pages document and correct all mistakes, especially
> > hard-to-quantify ones.
> > 
> > In the same document by Agner Fog, he says that he failed to confirm
> > 32-byte fetch on Fam16h CPUs:

So reportedly, the fetch window is 32-byte wide but I think there are
restrictions in the pipe elsewhere, which would have negative influence
on the actual throughput. And which could explain Agner's observations.
AFAICT.

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
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