On 03/05/2018 10:28 AM, Xueming Shen wrote:
On 03/05/2018 08:34 AM, Ian Rogers wrote:
Firstly, we're not running -Xcheck:jni in production code :-) During
development and testing it doesn't seem an unreasonable flag to enable, but
a 140x regression is too much to get developers to swallow.
There are 2 performance considerations:
1) the performance of -Xcheck:jni, which probably shouldn't be orders of
magnitude worse than without the flag.
2) the problems associated with JNI criticals, for which GetByteArrayRegion
is a panacea but by introducing a copying overhead.
The reason the GetByteArrayCritical was/is being used here is exactly to avoid
the copy
overhead, which was an issue escalated in the past. Though the "copy overhead"
appears
to be much bigger for the GBAC when -Xcheck:jni is used here.
Another issue with the DeflaterOutputStream is the default buf size is relative
too small,
for historical reason. So with a DeflaterOutStream(deflated, new Deflater(),
8192 *64),
is which a bigger buf/8192*64, the performance is close to the run with the
-Xcheck:jni
type:
in which a bigger buf/8192*64 is used, .... run without the -Xcheck:jni is
specified.
-Sherman
