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Re: __flush_cache_all() miscellany

To: "Kevin D. Kissell" <kevink@mips.com>
Subject: Re: __flush_cache_all() miscellany
From: Ralf Baechle <ralf@oss.sgi.com>
Date: Wed, 29 May 2002 14:28:55 -0700
Cc: Justin Carlson <justinca@cs.cmu.edu>, linux-mips@oss.sgi.com
In-reply-to: <01cb01c20754$4c14e400$10eca8c0@grendel>; from kevink@mips.com on Wed, May 29, 2002 at 11:03:20PM +0200
References: <1022691053.7644.16.camel@ldt-sj3-022.sj.broadcom.com> <1022700389.7644.155.camel@ldt-sj3-022.sj.broadcom.com> <01cb01c20754$4c14e400$10eca8c0@grendel>
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On Wed, May 29, 2002 at 11:03:20PM +0200, Kevin D. Kissell wrote:

> While trampolines, breakpointing and JITing are the main 
> uses of user-mode cache manipulation (drivers are a whole 
> 'nother story), we really should have distinct capabilities for 
> I-stream modification and for explicit synchronizations of 
> the data storage hierarchy, for non-coherent multiprocessors
> and user-manipulated DMA buffers.  As to whether
> those capabilities should be distinguished by system
> call (sysmips vs. cacheflush) or by parameter to the
> same system call, I don't have enough data to form
> an opinion at this point.

It should clearly be cacheflush(2); sysmips(2) is too coarse, too ugly
interface.  Another thing we'll still have to implement is the
cachectl(2) syscall; for certain systems and applications fine control
of the caching mode use for a memory mapping may result in major performance
improvments.

  Ralf

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