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[107.191.0.158]) by smtp.gmail.com with ESMTPSA id 136-v6sm21819itm.23.2018.07.10.11.51.56 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 10 Jul 2018 11:51:56 -0700 (PDT) Subject: Re: [PATCH 0/2] null_blk: zone support To: Bart Van Assche , "mb@lightnvm.io" , "loberman@redhat.com" Cc: "linux-kernel@vger.kernel.org" , "linux-block@vger.kernel.org" , Damien Le Moal References: <20180706173839.28355-1-mb@lightnvm.io> <1530899118.31977.1.camel@redhat.com> <296d2d14-0bf6-e0a2-84dc-7d6e819625c1@lightnvm.io> <4421a151-85d9-52e4-2233-03ed7f17528a@kernel.dk> <8d8ae6c620217db92b95b6561345d7bdf7c7cdfa.camel@wdc.com> <229911cb-7eb1-1729-46f1-35aba81d98d1@kernel.dk> <9225abd8-35de-641d-2d2b-7ed566fb9956@kernel.dk> From: Jens Axboe Message-ID: Date: Tue, 10 Jul 2018 12:51:55 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 7/10/18 12:49 PM, Bart Van Assche wrote: > On Tue, 2018-07-10 at 12:45 -0600, Jens Axboe wrote: >> The difference between the job file and the >> workload run can be huge. Consider something really basic: >> >> [randwrites] >> bs=4k >> rw=randwrite >> >> which would be 100% random 4k writes. If I run this on a zoned device, >> then that'd turn into 100% sequential writes. > > That's not correct. The ZBD code in the github pull request serializes writes > per zone, not globally. That's a totally minor detail. If all my random writes fall within a single zone, then they'd be 100% sequential. For N open zones, you'd be 100% sequential within the zone. The point is that the workload as defined and the workload as run are two totally different things, and THAT is the problem. -- Jens Axboe