RFR(M): 8249963: Make the zlib implementation selectively configurable at startup

[Alan Bateman]

On 23/07/2020 18:18, Volker Simonis wrote:
> Hi,
>
> can I please get some reviews for the following small enhancement
> which will allow you to configure different zlib implementations at VM
> start-up and get up to 100% better throughput for compression and
> about 50% better throughput for decompression (depending on the
> selected zlib implementation). We're using a similar change
> productively in Amazon since quite a while with good results on
> compression/decompression heavy workloads.
>
> As usual, my write-up is moch longer and much more complex than the
> change itself :)
Yes, this needs discussion and agreement before starting an RFR. As 
you've summarized in the JIRA issue, we have configure 
--with-zlib=system and --with-zlib=bundled today. The former is the way 
to build when what to make it possible to use an alternative zlib.  The 
new requirement that I think you are brining up is the case where 
someone wants to use several zlib libraries at the same time, because 
they somehow know that one version has superior performance than the 
other on some functions. I think it's reasonable to ask if the JDK 
really needs to support this complexity. I could imagine testing or 
support folks in tears when they see the implications of this. Have you 
looked at alternatives that would benefit other users of zlib, e.g. an 
interposer that dispatches to the appropriate zlib based on configuration?

-Alan