RFR [10]: 8186517: sun.nio.cs.StandardCharsets$Aliases and ClassMap can be lazily loaded

[Martin Buchholz]

OK, but ...

I'd like to see further improvements here later, like switching to upper
case.

I just realized we have
java/nio/charset/StandardCharsets.java
sun/nio/cs/StandardCharsets.java

and they both have a UTF_8 field !



On Mon, Aug 21, 2017 at 11:53 AM, Claes Redestad <claes.redestad at oracle.com>
wrote:

>
> On 2017-08-21 20:05, Martin Buchholz wrote:
>
>> I agree we should optimize for common charset names, in part to help the
>> world move to UTF-8.
>>
>
> Agreed.
>
>
>> It's *weird* to canonicalize to lower case, when the canonical charset
>> names are all uppercase ("UTF-8" instead of "utf-8").
>>
>
> A pre-existing weirdness, and it goes deep enough that I haven't dared
> changing it.
>
>
>> ---
>>    62     public static final String UTF_8 = "UTF-8";
>> Is this still used?
>>
>> Maybe the very first thing lookup() should do is check
>> charsetName == UTF_8
>>
>
> Subsequent lookups are very likely to hit the two-element cache in
> Charset, so I've not seen this add up.
>
>
>> ---
>>
>> Is switching from char[] to StringBuilder really an improvement?  Charset
>> names are all short, so the cost of copying the char[] to a byte[] is
>> negligible.
>>
>
> This allows us to not load and touch the code to deflate a char[] to a
> byte[] (StringUTF16), so a tiny, tiny startup win. Throughput-wise it's
> likely no different.
>
> /Claes
>
>
>>
>> On Mon, Aug 21, 2017 at 6:46 AM, Claes Redestad <
>> claes.redestad at oracle.com <mailto:claes.redestad at oracle.com>> wrote:
>>
>>     Hi,
>>
>>     the Aliases and Classes inner classes in StandardCharsets can be
>>     lazily-loaded by restructuring how we check for the three
>>     default-loaded charsets. This removes some classloading and
>>     work from happening during critical phases of the VM startup,
>>     as well as a net gain on any systems that default to any of the
>>     three standard charsets (UTF-8, Latin-1, ASCII).
>>
>>     Webrev: http://cr.openjdk.java.net/~redestad/8186517/jdk.00/
>>     <http://cr.openjdk.java.net/%7Eredestad/8186517/jdk.00/>
>>     Bug: https://bugs.openjdk.java.net/browse/JDK-8186517
>>     <https://bugs.openjdk.java.net/browse/JDK-8186517>
>>
>>     I'm not sure if the pre-existing optimization to allow
>>     StandardCharsets.charsets() unsynchronized access to internals
>>     is really necessary (or even 100% correct), but by ensuring we
>>     retrieve the Aliases and Classes instances in a synchronized block
>>     we should be no worse off semantically here.
>>
>>     /Claes
>>
>>
>>
>
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