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Message-ID: <9a8748490602211402m7ab61633n3aa7ded63fa7bdcd@mail.gmail.com>
Date: Tue, 21 Feb 2006 23:02:09 +0100
From: "Jesper Juhl" <jesper.juhl@gmail.com>
To: "Paul Fulghum" <paulkf@microgate.com>
Subject: Re: make -j with j <= 4 seems to only load a single CPU core
Cc: "Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
       "Sam Ravnborg" <sam@ravnborg.org>, "Andrew Morton" <akpm@osdl.org>
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On 2/21/06, Paul Fulghum <paulkf@microgate.com> wrote:
> On Tue, 2006-02-21 at 22:10 +0100, Jesper Juhl wrote:
>
> > I should probably mention that the kernel I'm currently running and
> > observing this behaviour with is 2.6.16-rc4-mm1.
> ...
> > > I find this quite strange since anything from 'make -j 2' and up
> > > should be able to keep both cores resonably busy, but there seems to
> > > be a huge difference between j <= 4 and j > 4.
>
> I've seen the same thing (on Athlon 64x2 64 bit)
> but was not sure if it was a problem.
>
> The break point for me seems to be between -j 2 and -j 3

That's the break point for me as well when I'm not using 'nice'. When
I use 'nice' the break point moves to -j 4/5 .

> -j 2 = serialized (or the appearance of)
> -j 3 = both cores mostly busy
>
> I'm pretty sure with an earlier 2.6 kernel source (but same environment)
> I did not see this. I'll start back tracking to earlier kernels
> to see if I can identify when this started.
>

--
Jesper Juhl <jesper.juhl@gmail.com>
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