linux-kernel - Re: Can context switches be faster?

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Message-ID: <Pine.LNX.4.64.0610130950410.17368@turbotaz.ourhouse>
Date:	Fri, 13 Oct 2006 09:51:51 -0500 (CDT)
From:	Chase Venters <chase.venters@...entec.com>
To:	James Courtier-Dutton <James@...erbug.co.uk>
cc:	Arjan van de Ven <arjan@...radead.org>,
	John Richard Moser <nigelenki@...cast.net>,
	linux-kernel@...r.kernel.org
Subject: Re: Can context switches be faster?

On Fri, 13 Oct 2006, James Courtier-Dutton wrote:

> Arjan van de Ven wrote:
>> On Thu, 2006-10-12 at 14:25 -0400, John Richard Moser wrote:
>>
>>
>>>   - Does the current code act on these behaviors, or just flush all
>>>     cache regardless?
>>
>> the cache flushing is a per architecture property. On x86, the cache
>> flushing isn't needed; but a TLB flush is. Depending on your hardware
>> that can be expensive as well.
>>
>
> So, that is needed for a full process context switch to another process.
> Is the context switch between threads quicker as it should not need to
> flush the TLB?

Indeed. This is also true for switching from a process to a kernel thread 
and back, because kernel threads don't have their own user-space virtual 
memory; they just live inside the kernel virtual memory mapped into every 
process.

> James
>

Thanks,
Chase
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