Improve performance of ASM's ClassReader.readStream() #26665
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Hello,
ClassReader.readStream()
can be reworked to improve its performance and reduce memory consumption. Currently there are two major problems about it:InputStream
byte[]
underlying inByteArrayOutputStream
Using
InputStream.available()
we can pre-size the buffer in vast majority of cases and even when the whole data is not read within one iteration (for largeInputStreams
) we allocate as much memory as required.Another optimization is about checking whether it was only one read from
InputStream
, and in this case the buffer itself can be returned instead of callingByteArrayOutputStream.toByteArray()
.I've used this benchmark available here to check impact of the patch for start-up of simple Spring Boot application:
and got the following results: