From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Message-ID: <53236D0B.5040507@kernel.dk> Date: Fri, 14 Mar 2014 14:56:43 -0600 From: Jens Axboe MIME-Version: 1.0 Subject: Re: Possible bug when setting compression References: <532349BF.4010307@kernel.dk> <532361FE.10901@kernel.dk> <53236538.2040903@kernel.dk> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit To: Matthew Eaton Cc: fio@vger.kernel.org List-ID: On 03/14/2014 02:53 PM, Matthew Eaton wrote: >> So that wont work as-is, since the parser will bypass the store when the >> callback is specified. It needs a one-liner, please try this updated one >> instead. >> >> -- >> Jens Axboe >> > > Ok, so it looks like everything works now except for zero_buffers. > > fio-2.1.6.1-11-g0574 + patch > > buffer_compress_percentage=100 > iops=83457 > > buffer_compress_percentage=50 > iops=78836 > > buffer_compress_percentage=1 > iops=52785 > > buffer_compress_percentage=0 > iops=51013 > > zero_buffers > iops=69465 > > scramble_buffers=0 > zero_buffers > iops=83451 zero_buffers and buffer_compres_percentage=100 are essentially the same thing, for both cases it writes buffers just fill of zeroes. So I'm not sure what you were expecting here since you don't think it works as it should? If you have both zero_buffers and scramble set, then the result will be a bit less compressible. The goal of scramble_buffers is to defeat basic dedupe attempts. So even if you don't fully refill your buffers every time, the blocks will be a bit different. -- Jens Axboe