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Date: Thu, 03 Mar 2005 22:37:19 +0800
From: David Xu <davidxu@freebsd.org>
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To: Ryan Sommers <ryans@gamersimpact.com>
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cc: arch@freebsd.org
cc: David Schultz <das@freebsd.org>
Subject: Re: Removing kernel thread stack swapping
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Ryan Sommers wrote:

> David Schultz wrote:
>
>> Any objections to the idea of removing the feature of swapping out
>> kernel stacks?  Unlike disabling UAREA swapping, this has the
>> small downside that it wastes 16K (give or take a power of 2) of
>> wired memory per kernel thread that we would otherwise have
>> swapped out.  However, this disadvantage is probably negligible by
>> today's standards, and there are several advantages:
>
>
> I like the idea of fixing a lot of possible panics. However, I don't 
> know if we should nix it completely. Wasting this little memory won't 
> hurt anyone on a contemporary computer. However, our embedded systems 
> folks don't look at memory in the same light, and 16K here or there 
> can begin to really add up in a memory tight architecture. Of course 
> it could be argued that embedded systems probably don't have many 
> threads, many threads that can be swapped, or even swap space in the 
> first place.
>
> I guess it's a judgment call that one of our embedded systems 
> engineers could better answer.
>
Does your embedded system has swap device ? I have joined some embedded
projects in the company, and there is no swap devices at all, no HDD
etcs, just a CF card or flash memory card and swap is totally turned off.

David Xu