linux-kernel - Re: [RFC 0/3] Basic support for LWP

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Message-ID: <alpine.LFD.2.00.1010051730060.2556@localhost6.localdomain6>
Date:	Tue, 5 Oct 2010 17:34:11 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Hans Rosenfeld <hans.rosenfeld@....com>
cc:	robert.richter@....com, LKML <linux-kernel@...r.kernel.org>,
	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...e.hu>,
	"Herrmann3, Andreas" <Andreas.Herrmann3@....com>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [RFC 0/3] Basic support for LWP

On Tue, 5 Oct 2010, Hans Rosenfeld wrote:

> [ adding Robert ]
> 
> On Mon, Oct 04, 2010 at 06:13:46PM -0400, Thomas Gleixner wrote:
> > > LWP (Light-Weight Profiling) is a new profiling mechanism that allows
> > > user mode processes to gather performance data about themselves with
> > > very low overhead. The specification can be found here:
> > >         http://developer.amd.com/cpu/LWP/Pages/default.aspx
> > 
> > All I can see there is marketing blurb. The spec pdf does not tell me
> > either how the end result of your patches will look like.
> 
> Well, you should get a basic understanding of how LWP works from the
> spec. I'm pretty sure there is more than that blurb in there.
> 
> What I sent _is_ the end result. Supporting LWP in the task switching
> code is the only thing necessary to use the LWP instructions in user
> space. And that is also what I'd like to get some comments on.

So it's the end result. Ok, then explain the following sentence:
 
> > > This code adds basic support for LWP to the context switch code, which
> > > is the minimum needed to use LWP. Support for other LWP features like
> > > interrupts will be added later.

If your patch _IS_ the end result then there are no other LWP
features, right ?

If there are, then your patch is _NOT_ the end result and we really
want to know what is coming.

Thanks,

	tglx
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