Message-ID: <452E8980.5040504@comcast.net>
Date: Thu, 12 Oct 2006 14:29:20 -0400
From: John Richard Moser <nigelenki@comcast.net>
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To: Phillip Susi <psusi@cfl.rr.com>
CC: linux-kernel@vger.kernel.org
Subject: Re: Can context switches be faster?
References: <452E62F8.5010402@comcast.net> <452E876F.1000604@cfl.rr.com>
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Phillip Susi wrote:
> John Richard Moser wrote:
>> Can context switches be made faster?  This is a simple question, mainly
>> because I don't really understand what happens during a context switch
>> that the kernel has control over (besides storing registers).
>>
> 
> Besides saving the registers, the expensive operation in a context
> switch involves flushing caches and switching page tables.  This can be
> avoided if the new and old processes both share the same address space.
> 

i.e. this can be avoided when switching to threads in the same process.

How does a page table switch work?  As I understand there are PTE chains
which are pretty much linked lists the MMU follows; I can't imagine this
being a harder problem than replacing the head.  I'd imagine the head
PTE would be something like a no-access page that's not really mapped to
anything so exchanging it is pretty much exchanging its "next" pointer?


> 
> 

- --
    We will enslave their women, eat their children and rape their
    cattle!
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