RFR: 8175891, 8192892: JrtPath improvements

[Claes Redestad]

Jim, Sundar,

thanks for the quick reviews!

/Claes


On 2017-12-01 14:53, Sundararajan Athijegannathan wrote:
> +1
>
> -Sundar
>
> On 01/12/17, 7:04 PM, Claes Redestad wrote:
>> Hi,
>>
>> please review this patch that resolves two small but sometimes 
>> significant inefficiencies in jdk.internal.jrtfs.JrtPath:
>>
>> Improve JrtPath::getResolved fast-path test:
>> https://bugs.openjdk.java.net/browse/JDK-8192892
>>
>> Testing for '.' is insufficient as it's likely all paths have a dot 
>> in them, while resolving is rare. Patch uses a test that is logically 
>> equivalent to that in ZipPath::getResolved to better filter out paths 
>> that don't need to take the slow path.
>>
>> JrtPath::resolve off-by-one pre-sizing cause for memory pressure:
>> https://bugs.openjdk.java.net/browse/JDK-8175891
>>
>> As path is normalized to never end with a / this code can be simplified.
>>
>> Webrev: http://cr.openjdk.java.net/~redestad/8192892/open.0/
>>
>> In a JMH micro[1] that naively walks all entries in the JDK 
>> lib/modules and counts classes, these fixes work together to remove 
>> overhead both in repeated and single-shot settings (the latter is 
>> relevant since jrtfs usage may influence startup times in certain 
>> applications and tools):
>>
>> Benchmark           Mode  Cnt  Score   Error  Units
>> JRTWalk.walkJImage  avgt   25  0.049 ± 0.003   s/op
>> JRTWalk.walkJImage  avgt   25  0.027 ± 0.001   s/op  # 1.8x
>>
>> Benchmark           Mode  Cnt  Score   Error  Units
>> JRTWalk.walkJImage    ss   20  0.436 ± 0.018   s/op  (best: 0.389 s/op)
>> JRTWalk.walkJImage    ss   20  0.388 ± 0.017   s/op  (best: 0.363 s/op)
>>
>> Thanks!
>>
>> /Claes
>>
>> [1] http://cr.openjdk.java.net/~redestad/8192892/JRTWalk.java