From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from merlin.infradead.org ([205.233.59.134]:47609 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933295Ab3ECRip (ORCPT ); Fri, 3 May 2013 13:38:45 -0400 Date: Fri, 3 May 2013 19:38:26 +0200 From: Jens Axboe Subject: Re: random read generates zero filled file Message-ID: <20130503173826.GX7800@kernel.dk> References: <82C5A0D6-2960-41B7-89B6-1D8C72D011C0@ulb.ac.be> <20130503100839.GI7800@kernel.dk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130503100839.GI7800@kernel.dk> Sender: fio-owner@vger.kernel.org List-Id: fio@vger.kernel.org To: Michel Jansens Cc: fio@vger.kernel.org On Fri, May 03 2013, Jens Axboe wrote: > On Fri, May 03 2013, Michel Jansens wrote: > > Hi, > > > > I'm trying out FIO, and rand a random read job with a 12GB file. It > > seems that the "Laying out IO file(s) " process generates a > > zero-filled file. This means that when compression is activated (on > > ZFS), no reads actually happens. > > > > I tried adding a "buffer_compress_percentage=10" section to tell > > generated data should compress from only "10%" but this seems to apply > > only to actual benchmark job, not the 'laying out file's. > > > > Am I missing something? > > No, it currently just fills zeroes. It's trivial to make it honor the > usual buffer fill logic, though. With the below patch, it'll do what fio > otherwise would have done to IO buffers during the benchmark run. Since the followups didn't make it here, the below exposed a bug in the compression logic where it would loop infinitely if compress_chunk wasn't set too. So we got a new feature, and a fix for an older bug as well. Commit is here: http://git.kernel.dk/?p=fio.git;a=commit;h=cc86c395fd9dd2002ec1edc0967b7c9453debdfb -- Jens Axboe