Apparent performance regression 8.3@ -> 8.4 at r255966?

[Julian Elischer]

On 10/10/13 10:02 PM, Ivan Voras wrote:
> On 07/10/2013 19:28, David Wolfskill wrote:> At work, we have a bunch of
> machines that developers use to build some
>> software.  The machines presently run FreeBSD/amd64 8.3-STABLE @rxxxxxx
>> (with a few local patches, which have since been committed to stable/8),
>> and the software is built within a 32-bit jail.
>>
>> The hardware includes 2 packages of 6 physical cores each @3.47GHz
>> (Intel X5690); SMT is enabled (so the scheduler sees hw.ncpu ==
>> 24).  The memory on the machines was recently increased from 6GB
>> to 96GB.
>>
>> I am trying to set up a replacement host environment on my test machine;
>> the current environment there is FreeBSD/amd64 8.4-STABLE @r255966; this
>> environment achieves a couple of objectives:
>>
>> * It has no local patches.
>> * The known problems (e.g., with mfiutil failing to report battery
>>    status accurately) are believed to be addressed appropriately.
>>
>> However: when I do comparison software builds, the new environment is
>> taking about 12% longer to perform the same work (comparing against a
>> fair sample of the deployed machines):
> So, the test machine is exactly the same as the old machines? Does the
> hardware upgrade coincide with 8.4-STABLE upgrade?
>
> At a guess, you also might be hitting a problem with either NUMA (which
> would mean the difference you encountered is pretty much random,
> depending on how the memory from your processes was allocated), or a
> generic scheduler issue (IIRC, FreeBSD 9 series was found to be much
> more scalable for > 16 CPUs).
>
> Just a thought - you *could* set up an 8-STABLE jail in a 9-STABLE
> environment if you need the 8-STABLE libraries for your software.
>
>
>
OR,
take the new kernel and use it to boot the old system
then compare times.