RFR: 8207005 : Disable the file canonicalization cache by default

[Alan Bateman]

On 10/07/2018 22:02, Brent Christian wrote:
> Hi,
>
> Please review this change to disable the file canonicalization cache 
> by default.
>
> Bug:
> https://bugs.openjdk.java.net/browse/JDK-8207005
>
> From the bug report:
> "The file canonicalization cache was added back in JDK 1.4.2 in order 
> to improve startup time.
>
> The cache has long-standing correctness issues (JDK-7066948, for 
> example). For this reason, it has been desired to disable the cache by 
> default, but the increase to startup time was undesirable.
>
> Recent JDK releases have removed usages of the cache, in particular 
> from FilePermission (JDK-8164705 in JDK 9). This reduced usage of the 
> canonicalization cache should also reduce the startup effect of 
> disabling the cache by default. Measurements support this. Previous 
> measurements showed the startup effect of disabling the cache on Linux 
> to be 3-6%, depending on the specific benchmark. The same comparison 
> performed last month now shows no startup change on Linux.
>
> The file canonicalization cache can still be enabled by setting the 
> "sun.io.useCanonCaches" system property. This is merely a change to 
> the default value."
Happy to see this disabled as it has always been problematic. The patch 
looks okay although you don't of couse need to set the initial values to 
false.

-Alan