On 11/23/2015 03:15 PM, Matthew Eaton wrote:
I think this is an artifact of how gzip compression works, it doesn't
have an unlimited size window. It's 32k, iirc. Fio should fill so that
it ideally would compress to the given size with an ideal compression
algorithm.
You'd probably want to use buffer_compress_chunk=x to always force fio
to operate in sizes of that for compression, if you want to ensure that
gzip would be able to compress to the specified ratio. I do think we
have a loop missing though for that to do what you need, let me test
that and report back.
I think things should work for all sizes, if you add this patch and then add
buffer_compress_chunk=32k or similar to your job file. You can do that for
smaller block sizes as well, fio will use the minimum of that chunk size or
the write block size.
--
Jens Axboe
Applied the patch and added buffer_compress_chunk=32k and now it's
working for all block sizes. Thank you for the info and the patch!
Perfect, thanks for reporting and followup testing.
--
Jens Axboe
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