On Fri, Dec 13, 2019 at 05:10:10PM +0100, Zaslonko Mikhail wrote: > Hello, > > Could you please review the patch for btrfs below. > > Apart from falling back to 1 page, I have set the condition to allocate > 4-pages zlib workspace buffer only if s390 Deflate-Conversion facility > is installed and enabled. Thus, it will take effect on s390 architecture > only. > > Currently in zlib_compress_pages() I always copy input pages to the workspace > buffer prior to zlib_deflate call. Would that make sense, to pass the page > itself, as before, based on the workspace buf_size (for 1-page buffer)? Doesn't the copy back and forth kill the improvements brought by the hw supported decompression? > As for calling zlib_deflate with Z_FINISH flush parameter in a loop until > Z_STREAM_END is returned, that comes in agreement with the zlib manual. The concerns are about zlib stream that take 4 pages on input and on the decompression side only 1 page is available for the output. Ie. as if the filesystem was created on s390 with dflcc then opened on x86 host. The zlib_deflate(Z_FINISH) happens on the compresission side.
