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Re: LL/SC benchmarking [was: Mipsel libc with LL/SC online anywhere?]

To: Jun Sun <jsun@mvista.com>
Subject: Re: LL/SC benchmarking [was: Mipsel libc with LL/SC online anywhere?]
From: Johannes Stezenbach <js@convergence.de>
Date: Thu, 25 Jul 2002 21:24:51 +0200
Cc: "Kevin D. Kissell" <kevink@mips.com>, linux-mips@oss.sgi.com
In-reply-to: <3D4049D7.8090100@mvista.com>
Mail-followup-to: Johannes Stezenbach <js@convergence.de>, Jun Sun <jsun@mvista.com>, "Kevin D. Kissell" <kevink@mips.com>, linux-mips@oss.sgi.com
References: <00ce01c229a4$a7d4ed40$10eca8c0@grendel> <20020719123828.GA5521@convergence.de> <20020725162539.GA8804@convergence.de> <3D40302F.40806@mvista.com> <20020725184519.GB9302@convergence.de> <3D4049D7.8090100@mvista.com>
Sender: owner-linux-mips@oss.sgi.com
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On Thu, Jul 25, 2002 at 11:56:23AM -0700, Jun Sun wrote:
> Johannes Stezenbach wrote:
> >OTOH I doubt it's worth it to add the branch-likely hack to
> >stock glibc. How many people are using Linux/MIPS on embedded
> >CPU's without LL/SC?
> 
> There are probably more than you think.  The popuplar (and notorious) NEC 
> VR41xx family fall into this category.  I think at least one or two other 
> families of CPUs are like this too.

Ok, then maybe we should have /proc/sys/ entries where the kernel
tells glibc about CPU capabilities and kernel support for
userpace atomic operations, like:

- no /proc/sys/mips/* : use ll/sc (maybe emulated)
- have /proc/sys/mips/mips2-without-llsc: use branch-likely, read
  to get MAGIC_COOKIE to use
- have /proc/sys/mips/sony-ps2: whatever
- ...

Or use a sysmips() call to get the information.


Johannes


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