Re: [Pki-devel] [PATCH] 4 Replaced byte-to-char & char-to-byte converters.
On Wed, 2011-12-21 at 12:31 -0800, Andrew Wnuk wrote:
On 12/21/2011 11:23 AM, Ade Lee wrote:
>
>>> If there is an unacceptable degradation in performance, perhaps we could
>>> utilize some customized Java classes to perform these functions. As an
>>> alternative approach, as Endi alluded to, there is some ASN.1 code in
>>> Mozilla JSS, and speaking with Bob Relyea, we have been postulating on
>>> how much work would be involved to write JNI bindings via JSS to the
>>> ASN.1 encoders/decoders contained in NSS instead of moving this code to
>>> use java.nio.* classes. Theoretically, we may limit our performance
>>> issues in exchange for the extra work involved in making the effort to
>>> standardize on the NSS ASN.1 engine (although I don't know if this will
>>> resolve issues such as (3) noted above).
>>
>> I checked the code, it looks like some of Mozilla's JSS code also relies
>> on the Charset API. JNI calls have some overhead too, so we need to know
>> how it's going to be used to avoid negative performance impact.
>>
>
> I agree the performance is a concern, and is something that we should
> keep in mind, but it is not clear that differences in performance in
> these classes will degrade the performance of the system. The only way
> to determine where the system is really spending its time is by running
> it through a profiler and analyzing the results. We may find that the
> server spends comparatively no time in this code.
I think "may" is a proper keyword here. If someone, calls "Charset
API"
a "bottleneck" that should be good enough warning to do some simple
testing to verify it.
Lets say we do a simple test and the encoding takes 3 ms instead of 1 ms
to complete. What then? Do we reject the patch? Do we embark on a
process whereby we investigate custom code or look into JSS functions?
No - we do not. Why? Because we have no idea whether this is even a
bottleneck for our server. Just because it was a bottleneck for someone
else for some random app - does not mean it will be the same for us. It
may end up being a huge bottleneck - or it may be completely irrelevant.
We do not know - and we will not know - until we do profiling.
Without profiling information, we are optimizing in the dark, and we
will very likely spend a lot of wasted time optimizing the wrong things.
>
>
> On the other hand, we have a compelling reason to change these classes.
> The classes are deprecated - and will go away - and then everything will
> stop working.
>
> I suggest that we review this patch for correctness.
I think Matt's email was clear. This patch is fine but we had 3 concerns
which were listed in his email.
> Is the encoding
> correct?
There is no simple test to prove this or to replace years of
compatibility testing (case like (3) can be good example of this).
> Do the unit tests cover enough - or have the right inputs to
> validate the correctness of the conversion? It seems like there were
> situations like (3) where perhaps more testing is required.
Agreed, there was always apparent reason for fixes like (3).
>
>
> And we should schedule a performance testing and profiling task for next
> year. We will always have the 8.x code as a benchmark. If at that
> time, we find that these classes cause performance problems, we can
> always look into custom classes or maybe JSS code.
>
> It seems to me that talking about custom classes before having any
> profiling data is putting the cart before the horse.
>
> Ade
>
>