From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Message-ID: <547FCDC0.3000005@kernel.dk> Date: Wed, 03 Dec 2014 19:58:08 -0700 From: Jens Axboe MIME-Version: 1.0 Subject: Re: Repeat given pattern with buffer_compress_percentage References: <547FCA1C.1000808@kernel.dk> <547FCBC7.20309@kernel.dk> In-Reply-To: <547FCBC7.20309@kernel.dk> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit To: Karthick Srinivasachary , fio@vger.kernel.org List-ID: On 12/03/2014 07:49 PM, Jens Axboe wrote: > On 12/03/2014 07:42 PM, Jens Axboe wrote: >> On 12/03/2014 11:48 AM, Karthick Srinivasachary wrote: >>> Hi Folks, >>> >>> I have question. Any feedback appreciated..! >>> >>> With buffer_compress_percentage, fio writes random data + zeros. >>> >>> Is there a way to write random data + repeat_pattern (instead of >>> zero's). Pattern can be any user given pattern. >> >> We can just make it fill with buffer_pattern instead of zeroing. Given >> that the pattern is short enough, it should not skew the compression >> rate significantly. >> >> OK, did a quick patch and ran a quick test, looks like it's still within >> half a percent. >> >> Pull the latest -git, then apply the attached patch. That should do what >> you want. Please report back. > > Use this -v2 instead, it fixes a crash if you _don't_ set buffer_pattern... Updated documentation, everything is now in -git. So forget the patch, just git pull and try it out. Note the distinction on using refill_buffers=1 or not. If you don't set this, then each block will be compressible to the extent specified. But buffers are recycled, so whole device/file ratios might look different. If you want the compression percentage to apply across all blocks written, then you set refill_buffers=1 as well. -- Jens Axboe