Re: [PATCH] Use uname not sysctl to get the kernel revision

[Steve Munroe <sjmunroe@us.ibm.com>]

Theodore Tso <tytso@mit.edu> wrote on 07/12/2006 06:24:14 PM:

> On Wed, Jul 12, 2006 at 11:42:47AM -0600, Eric W. Biederman wrote:
> > Unless a darn good reason for keeping it is found, sys_sysctl won't be
> > in the kernel several months from now.  And uname is faster by a large
> > margin than /proc.
>
> Um, if glibc is using sys_sysctl, then that's a pretty good reason.
> Once we remove it from the kernel, then people will be forced to
> upgrade glibc's before they can install a newer kernel.  Can we please
> give people some time for an version of glibc with this change to make
> it out to most deployed systems, first?  It's really annoying when
> it's not possible to install a stock kernel.org kernel on a system,
> and often upgrading glibc is not a trivial thing to do on a
> distribution userspace, especially if there is a concern for ISV
> compatibility.  (Especially if C++ code is involved, unfortunately.)
>
We will need an implementation that will fall back to sys_sysctl for older
kernels. This is already common practice in glibc. I don't really
understand the performance concern because it seems to me that
_is_smp_system() is only called once per process.

But isn't this the kind of thing that the Aux Vector is for? I like vDSO
too, but I think it is best deployed for information of a more dynamic
nature and performance sensitive.



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