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Re: mips32_flush_cache routine corrupts CP0_STATUS with gcc-2.96

To: Carsten Langgaard <carstenl@mips.com>
Subject: Re: mips32_flush_cache routine corrupts CP0_STATUS with gcc-2.96
From: "Gleb O. Raiko" <raiko@niisi.msk.ru>
Date: Thu, 11 Jul 2002 14:36:21 +0400
Cc: Ralf Baechle <ralf@oss.sgi.com>, Jon Burgess <Jon_Burgess@eur.3com.com>, linux-mips@oss.sgi.com
Organization: NIISI RAN
References: <80256BF2.004ECBE6.00@notesmta.eur.3com.com> <20020711021554.A3207@dea.linux-mips.net> <3D2D465C.FA06D50A@niisi.msk.ru> <3D2D4D83.B2694DF1@mips.com> <3D2D58A6.2E5D9695@niisi.msk.ru> <3D2D5AD2.1B254721@mips.com>
Sender: owner-linux-mips@oss.sgi.com
Carsten Langgaard wrote:
> 
> "Gleb O. Raiko" wrote:
> > Basically, requirement of uncached run makes hadrware logic much simpler
> > and allows  to save silicon a bit.
> 
> That could be true, but then again I suggest making specific cache routines 
> for those
> CPUs.
> It would be a real performance hit for the rest of us, if we have to operate 
> from
> uncached space.
> 

In theory, yes, there is a performance penalty. In practice, I doubt
this penalty is significant. Sure, Linux likes to flush cahces, not to
say more. But, did somebody measure the penalty of uncached runs? Even
with microbencnmarks like lmbench.

Regards,
Gleb.


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