Re: SLUB: Use ilog2 instead of series of constant comparisons.

["Nish Aravamudan" <nish.aravamudan@gmail.com>]

On 6/6/07, Andrew Morton <akpm@linux-foundation.org> wrote:
> On Wed, 6 Jun 2007 11:36:07 -0700 (PDT) Christoph Lameter <clameter@sgi.com> wrote:
>
> > On Wed, 6 Jun 2007, Andrew Morton wrote:
> >
> > > This caused test.kernel.org's power4 build to blow up:
> > >
> > > http://test.kernel.org/abat/93315/debug/test.log.0
> > >
> > > fs/built-in.o(.text+0x148420): In function `.CalcNTLMv2_partial_mac_key':
> > > : undefined reference to `.____ilog2_NaN'
> >
> > Hmmm... Weird message that does not allow too much analysis.
> > The __ilog2_NaN comes about if 0 or a negative number is passed to ilog.
> > There is no way for that to happen since we check for KMALLOC_MIN_SIZE
> > and KMALLOC_MAX_SIZE in kmalloc_index() and an unsigned value is used.
> >
> > There is also nothing special in CalcNTLMv2_partial_mac_key(). Two
> > kmallocs of 33 bytes and 132 bytes each.
>
> Yes, the code all looks OK.  I suspect this is another case of the compiler
> failing to remove unreachable stuff.
>
> > Buggy compiler (too much stress on constant folding)? Or hardware? Can we
> > rerun the test?
>
> It happened multiple times:
> http://test.kernel.org/functional/pSeries-101_2.html
>
> I'm sure there's a way of extracting the compiler version out of
> test.kernel.org but I can't see it there.  Andy, maybe we should toss a gcc
> --version in there or something?

I went and looked at one of the GOOD jobs and acc'g to that, the gcc is

gcc version 3.3.3 (SuSE Linux)

(http://test.kernel.org/abat/93029/summary)

I agree, seems like it would be handy to spit that out somewhere nicer
and easier to get to. Maybe the machine links at the top should point
to a summary page which has a link to the .config, machine info, etc?
(more indirection, but may be ok).

Thanks,
Nish

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