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Re: __flush_cache_all() miscellany

To: "Maciej W. Rozycki" <macro@ds2.pg.gda.pl>
Subject: Re: __flush_cache_all() miscellany
From: Ralf Baechle <ralf@oss.sgi.com>
Date: Wed, 29 May 2002 15:46:24 -0700
Cc: Justin Carlson <justinca@cs.cmu.edu>, linux-mips@oss.sgi.com
In-reply-to: <Pine.GSO.3.96.1020529234323.17584P-100000@delta.ds2.pg.gda.pl>; from macro@ds2.pg.gda.pl on Wed, May 29, 2002 at 11:46:58PM +0200
References: <20020529143305.D888@dea.linux-mips.net> <Pine.GSO.3.96.1020529234323.17584P-100000@delta.ds2.pg.gda.pl>
Sender: owner-linux-mips@oss.sgi.com
User-agent: Mutt/1.2.5.1i
On Wed, May 29, 2002 at 11:46:58PM +0200, Maciej W. Rozycki wrote:

> > >  I converted a few flush_cache_all() invocations to __flush_cache_all() 
> > > where appropriate late last year, but the function is a bit older.  I
> > > think you might dig the linux-kernel list archives for a discussion on the
> > > semantics of flush_cache_all() (it's a nop for many MIPS CPUs) and
> > > friends.  The short description in Documentation/cachetlb.txt is a bit
> > > insufficient, I'm afraid. 
> > 
> > I don't like that function very much; it's sort of a shotgun approach
> > to flushing caches in a part of the kernel that's not too performance
> > relevant.  The whole interface sucks, should be replaced by something
> > more finegrained.
> 
>  Well, I suspect the API might be somewhat influenced by SPARC's oddities. 
> ;-) 

Historically that's certainly true.

As a general complaint about the style of interfaces of the cache stuff -
they're too low level.  Frequently we just don't know enough about the
situation to optimize the flush operation.

  Ralf

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