The CompressContent processor does not use the Compression Level property of the processor except for when using the GZIP compression format. On the contrary, the xz-lzma2 compression format defaults to using XZ compression level 6 for that specific format (I read the CompressContent.java source code to verify this) – disregarding whatever compression level you set on the processor itself.
As a side note, the xz compression format supports, amazingly enough, 10 levels of compression from 0 to 9 – the same as GZIP. The only difference that I can tell is level 0 of xz is not the lack of compression, but the lightest compression possible (i.e. still some compression) – whereas GZIP compression level 0 means just container the content but do not compress.
I have a use case where I must use the xz-lzma2 format (don't ask why) and I have to send (using the XZ format) already highly-compressed content that is XZ format to begin with. I have in excess of 500 GB of this sort of already highly compressed content to further compress into the XZ format on a daily basis.
The attached patch will enhance the CompressContent.java source code enabling the compression level property to be used in both the GZIP and the XZ-LZMA2 formats.
Please consider adding this patch to the baseline for this processor. I've tested it and the results are fantastic because I can crank down the compression level to 0 for XZ-LZMA2 now and use a lot less CPU. I'm generally seeing a 66% improvement in elapsed time to process highly compressed content using XZ format with compression level of 0 versus the hard-coded level 6 of the baseline code.