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

[Johannes Stezenbach <js@convergence.de>]

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