From: "Kevin D. Kissell" <kevink@mips.com>
To: "Jun Sun" <jsun@mvista.com>
Cc: <linux-mips@linux-mips.org>
Subject: Re: [jsun@mvista.com: Re: [RFC] FPU context switch]
Date: Wed, 18 Sep 2002 10:45:08 +0200 [thread overview]
Message-ID: <004101c25eef$ba035350$10eca8c0@grendel> (raw)
In-Reply-To: 20020917171434.Q17321@mvista.com
From: "Jun Sun" <jsun@mvista.com>
> On Wed, Sep 18, 2002 at 02:10:17AM +0200, Kevin D. Kissell wrote:
> > Are you able to test this stuff on a proper SMP
> > system, by the way? The efficiency of the code
> > that manipulates interprocessor control variables
> > can reasonably be expected to drop off a bit
> > in a system with MP cache invalidations blasting
> > left and right.
>
> Yes. I understand this effect. Solution 1), 2)
> and 3) don't really suffer from this problem because
> variables tested & manipulated are local - unless the
> process migrates which is a different problem.
It's not a "different problem", it's the heart of the
problem. If we weren't worried about SMP
behavior, we wouldn't be revisiting this stuff.
While (1) can obviously be done without any
global knowledge, as could something (2)-like
based on CPU-local state such as Status.CU1,
(2), (3) and (4), as you describe them, all depend
to some degree on shared multiprocessor variables
to determine whether to save or restore FP state.
Regards,
Kevin K.
WARNING: multiple messages have this Message-ID (diff)
From: "Kevin D. Kissell" <kevink@mips.com>
To: Jun Sun <jsun@mvista.com>
Cc: linux-mips@linux-mips.org
Subject: Re: [jsun@mvista.com: Re: [RFC] FPU context switch]
Date: Wed, 18 Sep 2002 10:45:08 +0200 [thread overview]
Message-ID: <004101c25eef$ba035350$10eca8c0@grendel> (raw)
Message-ID: <20020918084508.U6Z1YAmRdG6FHhGZnxNUsDah-_x3u6jFQ1Y72JKOwF8@z> (raw)
In-Reply-To: 20020917171434.Q17321@mvista.com
From: "Jun Sun" <jsun@mvista.com>
> On Wed, Sep 18, 2002 at 02:10:17AM +0200, Kevin D. Kissell wrote:
> > Are you able to test this stuff on a proper SMP
> > system, by the way? The efficiency of the code
> > that manipulates interprocessor control variables
> > can reasonably be expected to drop off a bit
> > in a system with MP cache invalidations blasting
> > left and right.
>
> Yes. I understand this effect. Solution 1), 2)
> and 3) don't really suffer from this problem because
> variables tested & manipulated are local - unless the
> process migrates which is a different problem.
It's not a "different problem", it's the heart of the
problem. If we weren't worried about SMP
behavior, we wouldn't be revisiting this stuff.
While (1) can obviously be done without any
global knowledge, as could something (2)-like
based on CPU-local state such as Status.CU1,
(2), (3) and (4), as you describe them, all depend
to some degree on shared multiprocessor variables
to determine whether to save or restore FP state.
Regards,
Kevin K.
next prev parent reply other threads:[~2002-09-18 8:43 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-09-17 23:04 [jsun@mvista.com: Re: [RFC] FPU context switch] Jun Sun
2002-09-18 0:10 ` Kevin D. Kissell
2002-09-18 0:10 ` Kevin D. Kissell
2002-09-18 0:14 ` Jun Sun
2002-09-18 8:45 ` Kevin D. Kissell [this message]
2002-09-18 8:45 ` Kevin D. Kissell
2002-09-18 16:57 ` Jun Sun
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