Messages in this thread | | | Date | Wed, 12 Jul 2006 14:29:43 -0700 | From | "H. Peter Anvin" <> | Subject | Re: [PATCH] Use uname not sysctl to get the kernel revision |
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Eric W. Biederman wrote: > "H. Peter Anvin" <hpa@zytor.com> writes: > >> Jakub Jelinek wrote: >>> On Wed, Jul 12, 2006 at 12:33:56PM -0700, Ulrich Drepper wrote: >>>> Roland McGrath wrote: >>>>> We could also put the uname info (modulo nodename) into the vDSO. >>>> Or even better: real topology information. >>> AND rather than OR would be even better. So glibc could find kernel >>> version, etc. and topology in the vDSO cheaply. >> Wouldn't it make more sense for this to be in ELF tags, rather than the vdso? >> Another alternative, I guess, would be to put a pointer in the ELF tags, which >> may point into the vdso. > > Cheap and simple access to topology information would be interesting. > > Glibc just wants to know if our kernel is SMP so it can know if it is > ok to busy wait for a bit waiting for a mutex. Or if busy waiting is > a complete loss. > > The practical challenge is that topology information is not fixed but > potentially varies at runtime. > > Ulrich what would be interesting besides the possibility of having > multiple cpus? >
Something that might make sense to ask CPU vendors for in the future: an instruction that can either trap or be a noop (or better, cpu_relax) based on a control register.
Not that that solves any problem any time soon.
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