Subject: Re: Interrupt starvation points
From: Daniel Walker <dwalker@mvista.com>
Reply-To: dwalker@mvista.com
To: Russell King <rmk+lkml@arm.linux.org.uk>
Cc: linux-kernel@vger.kernel.org
In-Reply-To: <20050211200424.B28971@flint.arm.linux.org.uk>
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	 <20050211200424.B28971@flint.arm.linux.org.uk>
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Date: 11 Feb 2005 13:52:19 -0800
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On Fri, 2005-02-11 at 12:04, Russell King wrote:
> 
> Please substantiate your claim that up() is very expensive on ARM.
> I disagree:

	I should have made it clear that I was talking about the RT version of
up() . The RT version doesn't have any assembly in it, and it is
expensive. 

> Plus, after you've read the above code, wouldn't you think that adding
> the "enable interrupts + disable interrupts" around an up() operation
> (which itself immediately disables interrupts again) is just adding
> extra instructions to the kernel, which corresponds directly to lower
> performance?

	Not in the RT case. However, I never said that was a proper fix, I was
just producing code that helped in my tests.

Daniel

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