Compression levels and defaults
The compression level is a measure of the compression quality. It is expressed as an integer in the range 1 - 9.
Compression quality and performance are conflicting goals. Compression level 1 provides best performance at the expense of quality. Compression level 9 provides the best quality at the expense of performance. The compression level that is provided by the Integrated Accelerator for zEDC is approximately equivalent to level 1.
Acceleration defaults
The following defaults apply to both on-chip acceleration for gzip and zlib in user space and for
the kernel zlib:
- By default, decompression is accelerated.
- By default, compression is accelerated only if compression level 1 is requested.
Expanding the scope of compression acceleration
Configure software with a configurable compression level to request level 1 to enable on-chip compression.
For other types of software you must configure the on-chip accelerator.
- Software that hardcodes a compression level other than 1.
- Software that neither requests a particular level nor provides an option to configure a level. Such software requests level 6 by default.
If level 1 compression is acceptable for your purposes, use overrides to apply on-chip
compression to any requested compression level:
- For applications in user space, including Java™ workloads, see Overrides for applications.
- For the kernel, see Overrides for the kernel zlib.