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While portions of the code needed to support z_compress_level() and z_uncompress() where in place. In reality the current implementation was non-functional, it just was compilable. The critical missing component was to setup a workspace for the compress/uncompress stream structures to use. A kmem_cache was added for the workspace area because we require a large chunk of memory. This avoids to need to continually alloc/free this memory and vmap() the pages which is very slow. Several objects will reside in the per-cpu kmem_cache making them quick to acquire and release. A further optimization would be to adjust the implementation to additional ensure the memory is local to the cpu. Currently that may not be the case.
The Solaris Porting Layer (SPL) is a Linux kernel module which provides many of the Solaris kernel APIs. This shim layer makes it possible to run Solaris kernel code in the Linux kernel with relatively minimal modification. This can be particularly useful when you want to track upstream Solaris development closely and don’t want the overhead of maintaining a large patch which converts Solaris primitives to Linux primitives.
To build packages for your distribution:
$ ./configure
$ make pkg
Full documentation for building, configuring, and using the SPL can be found at: http://zfsonlinux.org