From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from pasmtpb.tele.dk ([80.160.77.98]:58150 "EHLO pasmtpB.tele.dk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753003AbYKSNpB (ORCPT ); Wed, 19 Nov 2008 08:45:01 -0500 Date: Wed, 19 Nov 2008 14:43:13 +0100 From: Jens Axboe Subject: Re: Help required to understand fio output Message-ID: <20081119134313.GF26308@kernel.dk> References: <4924115E.6040701@seanodes.com> <20081119131945.GD26308@kernel.dk> <492417BC.1020701@seanodes.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <492417BC.1020701@seanodes.com> Sender: fio-owner@vger.kernel.org List-Id: fio@vger.kernel.org To: Erwan Velu Cc: fio@vger.kernel.org On Wed, Nov 19 2008, Erwan Velu wrote: > Jens Axboe wrote: > > [...] > >The output could do with a bit of prettying up... It's explained in the > >documentation, though, The 100=64.24% field means that 64.24% of the ios > >completed within 50 and 99ms, as you indicate. > > > I would say that [50-99]=64.24% would have been less confusing even if > it take more room. > [...] That's the primary problem, but I guess it's just to compressed for its own good... > >>And then, how should I understan lines 8 & 9 that reports that 100% of > >>IOs were completed with a depth=4... What happened ? > >> > > > >Same deal, 4 means 1-4 completions per io_getevents() call for your test > >case. So any attempt to retrieve completed IO from the system resulted > >in a return of 1-4 ios. > I just don't understand what the reason of that 64 -> 4 depth reduction. > Is that related to the storage or the kernel capabilities ? If you don't tell fio otherwise, it'll attempt to reclaim completed IO as soon as it can. You can control this behaviour with the iodepth_* options. -- Jens Axboe