Re: Bug with --buffer_compress_percentage

[Jens Axboe <axboe@kernel.dk>]

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