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

[Andy Whitcroft <apw@shadowen.org>]

Andy Whitcroft wrote:
> Nish Aravamudan wrote:
>> 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).
> 
> They probably should be replicated with the job as the machine may
> change compiler at some time in its life.  If for no other reason that
> there should be a break in the kernbench graph if it does ... :)

Ok, the compiler.ver file should be replicated out with new jobs now and
can be found with the dotconfig file in the build directory.

-apw

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