• Mikhail Zaslonko's avatar
    lib/zlib: add s390 hardware support for kernel zlib_deflate · aa5b395b
    Mikhail Zaslonko authored
    Patch series "S390 hardware support for kernel zlib", v3.
    
    With IBM z15 mainframe the new DFLTCC instruction is available.  It
    implements deflate algorithm in hardware (Nest Acceleration Unit - NXU)
    with estimated compression and decompression performance orders of
    magnitude faster than the current zlib.
    
    This patchset adds s390 hardware compression support to kernel zlib.
    The code is based on the userspace zlib implementation:
    
    	https://github.com/madler/zlib/pull/410
    
    The coding style is also preserved for future maintainability.  There is
    only limited set of userspace zlib functions represented in kernel.
    Apart from that, all the memory allocation should be performed in
    advance.  Thus, the workarea structures are extended with the parameter
    lists required for the DEFLATE CONVENTION CALL instruction.
    
    Since kernel zlib itself does not support gzip headers, only Adler-32
    checksum is processed (also can be produced by DFLTCC facility).  Like
    it was implemented for userspace, kernel zlib will compress in hardware
    on level 1, and in software on all other levels.  Decompression will
    always happen in hardware (when enabled).
    
    Two DFLTCC compression calls produce the same results only when they
    both are made on machines of the same generation, and when the
    respective buffers have the same offset relative to the start of the
    page.  Therefore care should be taken when using hardware compression
    when reproducible results are desired.  However it does always produce
    the standard conform output which can be inflated anyway.
    
    The new kernel command line parameter 'dfltcc' is introduced to
    configure s390 zlib hardware support:
    
        Format: { on | off | def_only | inf_only | always }
         on:       s390 zlib hardware support for compression on
                   level 1 and decompression (default)
         off:      No s390 zlib hardware support
         def_only: s390 zlib hardware support for deflate
                   only (compression on level 1)
         inf_only: s390 zlib hardware support for inflate
                   only (decompression)
         always:   Same as 'on' but ignores the selected compression
                   level always using hardware support (used for debugging)
    
    The main purpose of the integration of the NXU support into the kernel
    zlib is the use of hardware deflate in btrfs filesystem with on-the-fly
    compression enabled.  Apart from that, hardware support can also be used
    during boot for decompressing the kernel or the ramdisk image
    
    With the patch for btrfs expanding zlib buffer from 1 to 4 pages (patch
    6) the following performance results have been achieved using the
    ramdisk with btrfs.  These are relative numbers based on throughput rate
    and compression ratio for zlib level 1:
    
      Input data              Deflate rate   Inflate rate   Compression ratio
                              NXU/Software   NXU/Software   NXU/Software
      stream of zeroes        1.46           1.02           1.00
      random ASCII data       10.44          3.00           0.96
      ASCII text (dickens)    6,21           3.33           0.94
      binary data (vmlinux)   8,37           3.90           1.02
    
    This means that s390 hardware deflate can provide up to 10 times faster
    compression (on level 1) and up to 4 times faster decompression (refers
    to all compression levels) for btrfs zlib.
    
    Disclaimer: Performance results are based on IBM internal tests using DD
    command-line utility on btrfs on a Fedora 30 based internal driver in
    native LPAR on a z15 system.  Results may vary based on individual
    workload, configuration and software levels.
    
    This patch (of 9):
    
    Create zlib_dfltcc library with the s390 DEFLATE CONVERSION CALL
    implementation and related compression functions.  Update zlib_deflate
    functions with the hooks for s390 hardware support and adjust workspace
    structures with extra parameter lists required for hardware deflate.
    
    Link: http://lkml.kernel.org/r/20200103223334.20669-2-zaslonko@linux.ibm.comSigned-off-by: default avatarIlya Leoshkevich <iii@linux.ibm.com>
    Signed-off-by: default avatarMikhail Zaslonko <zaslonko@linux.ibm.com>
    Co-developed-by: default avatarIlya Leoshkevich <iii@linux.ibm.com>
    Cc: Chris Mason <clm@fb.com>
    Cc: Christian Borntraeger <borntraeger@de.ibm.com>
    Cc: David Sterba <dsterba@suse.com>
    Cc: Eduard Shishkin <edward6@linux.ibm.com>
    Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
    Cc: Josef Bacik <josef@toxicpanda.com>
    Cc: Richard Purdie <rpurdie@rpsys.net>
    Cc: Vasily Gorbik <gor@linux.ibm.com>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    aa5b395b
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