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Date:      Tue, 7 Aug 2001 03:18:32 -0400
From:      Bosko Milekic <bmilekic@technokratis.com>
To:        Terry Lambert <tlambert2@mindspring.com>
Cc:        Matt Dillon <dillon@earth.backplane.com>, Zhihui Zhang <zzhang@cs.binghamton.edu>, freebsd-hackers@FreeBSD.ORG
Subject:   Re: Allocate a page at interrupt time
Message-ID:  <20010807031832.A46112@technokratis.com>
In-Reply-To: <3B6F8A6C.B95966B7@mindspring.com>; from tlambert2@mindspring.com on Mon, Aug 06, 2001 at 11:27:56PM -0700
References:  <Pine.SOL.4.21.0108031432070.28997-100000@opal> <200108051955.f75Jtk882156@earth.backplane.com> <3B6F8A6C.B95966B7@mindspring.com>

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On Mon, Aug 06, 2001 at 11:27:56PM -0700, Terry Lambert wrote:
> I keep wondering about the sagicity of running interrupts in
> threads... it still seems like an incredibly bad idea to me.
> 
> I guess my major problem with this is that by running in
> threads, it's made it nearly impossibly to avoid receiver
> livelock situations, using any of the classical techniques
> (e.g. Mogul's work, etc.).

	References to published works?
 
> It also has the unfortunate property of locking us into virtual
> wire mode, when in fact Microsoft demonstrated that wiring down
> interrupts to particular CPUs was good practice, in terms of
> assuring best performance.  Specifically, running in virtual

	Can you point us at any concrete information that shows this?
Specifically, without being Microsoft biased (as is most "data" published by
Microsoft)? -- i.e. preferably third-party performance testing that attributes
wiring down of interrupts to particular CPUs as _the_ performance advantage.

> wire mode means that all your CPUs get hit with the interrupt,
> whereas running with the interrupt bound to a particular CPU
> reduces the overall overhead.  Even what we have today, with

	Obviously.

> the big giant lock and redirecting interrupts to "the CPU in
> the kernel" is better than that...
> 
> -- Terry

-- 
 Bosko Milekic
 bmilekic@technokratis.com


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