On 3/5/18, 12:45 PM, Xueming Shen wrote:
On 3/5/18, 11:15 AM, Ian Rogers wrote:
Thanks! Changing the DeflaterOutputStream buffer size to be something
other than the default reduces the number of JNI native calls and is
a possible work around here, as this is an implementation detail
could it be made in the JDK? Unfortunately larger input sizes will
also regress the issue as the number of calls is "input size / buffer
size". The JNI critical may give direct access to the array but
depending on the GC, may require a lock and so lock contention may be
a significant issue with the code and contribute to tail latencies.
In my original post I mention this is difficult to measure and I
think good practice is to avoid JNI critical regions.
We do have a history on the usage of
GetPrimitiveArrayCritical/Elements() here regarding the
potential "lock contention", copy overhead... and went back and forth
on which jni call is the
appropriate one to go. Martin might still have the memory of that :-)
And for the record. The direct root trigger of this issue probably is
the fix for JDK-6311046 that went into jdk9.
https://bugs.openjdk.java.net/browse/JDK-6311046
-Sherman
