From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752213Ab3LSBG7 (ORCPT ); Wed, 18 Dec 2013 20:06:59 -0500 Received: from merlin.infradead.org ([205.233.59.134]:36213 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752002Ab3LSBG5 (ORCPT ); Wed, 18 Dec 2013 20:06:57 -0500 Message-ID: <52B246AC.1090107@infradead.org> Date: Wed, 18 Dec 2013 17:06:52 -0800 From: Randy Dunlap User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.0 MIME-Version: 1.0 To: Matias Bjorling , axboe@kernel.dk CC: linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/3] null_blk: documentation References: <1387370504-30853-1-git-send-email-m@bjorling.me> <1387370504-30853-2-git-send-email-m@bjorling.me> In-Reply-To: <1387370504-30853-2-git-send-email-m@bjorling.me> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/18/13 04:41, Matias Bjorling wrote: > Add description of module and its parameters. > > Signed-off-by: Matias Bjorling > --- > Documentation/block/null_blk.txt | 71 ++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 71 insertions(+) > create mode 100644 Documentation/block/null_blk.txt > > diff --git a/Documentation/block/null_blk.txt b/Documentation/block/null_blk.txt > new file mode 100644 > index 0000000..9e1b047 > --- /dev/null > +++ b/Documentation/block/null_blk.txt > @@ -0,0 +1,71 @@ > +Null block device driver > +================================================================================ > + > +I. Overview > + > +The null block device (/dev/nullb*) is used for benchmarking the various > +block-layer implementations. It emulates a block device of X gigabytes in size. > +The following instances are possible: > + > + Single-queue block-layer > + - Request-based. > + - Single submission queue per device. > + - Implements IO scheduling algorithms (CFQ, Deadline, noop). > + Multi-queue block-layer > + - Request-based. > + - Configurable submission queues per device. > + No block-layer (Known as bio-based) > + - Bio-based. IO requests are submitted directly to the device driver. > + - Directly accepts bio data structure and returns them. > + > +All of them has a completion queue for each core in the system. have The text sometimes uses "core" vs. "socket" vs. "cpu(s)". Did you double-check all of these uses? Thanks. > + > +II. Module parameters applicable for all instances: > + > +queue_mode=[0-2]: Default: 2-Multi-queue > + Selects which block-layer the module should instantiate with. > + > + 0: Bio-based. > + 1: Single-queue. > + 2: Multi-queue. > + > +home_node=[0--nr_nodes]: Default: NUMA_NO_NODE > + Selects what socket the data structures is allocated from. are > + > +gb=[Size in GB]: Default: 250GB > + The size of the device reported to the system. > + > +bs=[Block size (in bytes)]: Default: 512 bytes > + The block size reported to the system. > + > +nr_devices=[Num. devices]: Default: 2 Number > + Number of block devices instantiated. They are instantiated as /dev/nullb0, > + etc. > + > +irq_mode=[0-2]: Default: Soft-irq Default: 1-Soft-irq > + The completion mode used for completing IOs to the block-layer. > + > + 0: None. > + 1: Soft-irq. Uses ipi to complete IOs across sockets. Simulates the overhead IPI > + when IOs are issued from another socket than the home the device is > + connected to. > + 2: Timer: Waits a specific period (completion_nsec) for each IO before > + completion. > + > +completion_nsec=[Num. ns]: Default: 10.000ns Number > + Combined with irq_mode=2 (timer). The time each completion event must wait. > + > +submit_queues=[0..nr_cpus]: > + The number of submission queues attached to the device driver. If unset, it > + defaults to 1 on single-queue and bio-based instances. For multi-queue, > + its ignored when use_per_node_hctx module parameter is 1. it is > + > +hw_queue_depth=[0..qdepth]: Defaults: 64 Default: > + The hardware queue depth of the device. > + > +III: Multi-queue specific parameters > + > +use_per_node_hctx=[0/1]: Defaults: 1 Default: > + If 1, the multi-queue block layer is instantiated with a hardware dispatch > + queue for each CPU node in the system. If 0, it is instantiated with the > + number of queues defined in the submit_queues parameter. > -- ~Randy