Environment variables

The GenWQE hardware-accelerated zlib uses defaults that correspond to the following environment variable settings:

ZLIB_ACCELERATOR=GENWQE
ZLIB_CARD=-1
ZLIB_TRACE=0x0
ZLIB_DEFLATE_IMPL=0x41
ZLIB_INFLATE_IMPL=0x41

You can override these defaults by setting the following environment variables:

ZLIB_ACCELERATOR

Sets the accelerator type. For zEDC Express, the type is GENWQE.

ZLIB_CARD

-1, uses all accelerators that are available to the Linux® instance. Failed requests are retried on alternative accelerators.

You can specify the ID of a particular virtual accelerator card to be used. The ID is the index number that makes the nodes unique. All other cards are ignored, and no retry on alternative cards is performed if the specified card fails. Specify an ID only if you want to test a particular card.

0 uses the first card that is found by the device driver. As for specifying an individual card, all other cards are ignored.

ZLIB_TRACE

Sets tracing bits:

0x1

General trace.

0x2

Hardware trace.

0x4

Software trace.

0x8

Trace summary at the end of a process.

Tracing requires extra processing and incurs a performance penalty. The least performance impact is to be expected from the trace summary. By default, tracing is off.

ZLIB_DEFLATE_IMPL

0x01 and 0x41 enable hardware compression, where 0x41 adds an optimization setting. 0x00 forces software compression and is intended for experimentation, for example, for gathering performance data with and without hardware acceleration.

ZLIB_INFLATE_IMPL

0x01 and 0x41 enable hardware decompression, where 0x41 adds an optimization setting. 0x00 forces software decompression and is intended for experimentation, for example, for gathering performance data with and without hardware acceleration.

You can find more details about the environment variables in the GenWQE wiki on GitHub at github.com/ibm-genwqe/genwqe-user/wiki/Environment Variables.