Subject: Re: [PATCH 3/3] sched: Disable affine wakeups by default
From: Mike Galbraith <efault@gmx.de>
To: Arjan van de Ven <arjan@infradead.org>
Cc: Peter Zijlstra <peterz@infradead.org>, mingo@elte.hu,
       linux-kernel@vger.kernel.org
In-Reply-To: <20091025223657.5ebc2857@infradead.org>
References: <20091024125853.35143117@infradead.org>
	 <20091024130432.0c46ef27@infradead.org>
	 <20091024130728.051c4d7c@infradead.org>
	 <1256453725.12138.40.camel@marge.simson.net>
	 <20091025095109.449bac9e@infradead.org>
	 <1256492289.14241.40.camel@marge.simson.net>
	 <20091025123319.2b76bf69@infradead.org>
	 <1256508287.17306.14.camel@marge.simson.net>
	 <1256522035.7356.19.camel@laptop>
	 <1256531907.7117.31.camel@marge.simson.net>
	 <20091025215225.05ac9ac9@infradead.org>
	 <1256533734.7117.45.camel@marge.simson.net>
	 <20091025223657.5ebc2857@infradead.org>
Content-Type: text/plain
Date: Mon, 26 Oct 2009 06:47:58 +0100
Message-Id: <1256536078.7117.67.camel@marge.simson.net>
Mime-Version: 1.0
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1451
Lines: 34

On Sun, 2009-10-25 at 22:36 -0700, Arjan van de Ven wrote:
> On Mon, 26 Oct 2009 06:08:54 +0100
> Mike Galbraith <efault@gmx.de> wrote:

> > > 
> > > or we just use SD_WAKE_AFFINE / SD_BALANCE_WAKE for this...
> > 
> > I don't see how.  Oh, you mean another domain level, top level being
> > cache property, and turn off when degenerating?  That looks like it'd
> > be a problem, but adding SD_CACHE_SIBLING or whatnot should work.
> > Problem is how to gain knowledge of whether multicores share a cache
> > or not.
> 
> Actually I meant setting the SD_BALANCE_WAKE flag for the SMT and MC
> domains (and then making sure that "MC" really means "shares LLC" in
> the arch code), and then using this as indication in the sched code..

I don't think we can do that, because SD_WAKE_BALANCE already has a
different meaning.  SD_WAKE_AFFINE could be used though, affine wakeups
have always been a cache thing, and for trying to keep things affine to
a package or whatnot, we have SD_PREFER_LOCAL.  Sounds clean to me.

> if you're a multicore domain you better have a shared cache.. that's
> what it should mean. If it does not we should fix that.

Sounds reasonable to me.  I'll go make explosions.

	-Mike

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/