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From: Dave Chinner <david@fromorbit.com>
To: Shaohua Li <shaohua.li@intel.com>
Cc: linux-kernel@vger.kernel.org, axboe@kernel.dk, vgoyal@redhat.com,
	jmoyer@redhat.com
Subject: Re: [RFC 0/3]block: An IOPS based ioscheduler
Date: Wed, 4 Jan 2012 18:19:31 +1100	[thread overview]
Message-ID: <20120104071931.GB17026@dastard> (raw)
In-Reply-To: <20120104065337.230911609@sli10-conroe.sh.intel.com>

On Wed, Jan 04, 2012 at 02:53:37PM +0800, Shaohua Li wrote:
> An IOPS based I/O scheduler
> 
> Flash based storage has some different characteristics against rotate disk.
> 1. no I/O seek.
> 2. read and write I/O cost usually is much different.
> 3. Time which a request takes depends on request size.
> 4. High throughput and IOPS, low latency.
> 
> CFQ iosched does well for rotate disk, for example fair dispatching, idle
> for sequential read. It also has optimization for flash based storage (for
> item 1 above), but overall it's not designed for flash based storage. It's
> a slice based algorithm. Since flash based storage request cost is very
> low, and drive has big queue_depth is quite popular now which makes
> dispatching cost even lower, CFQ's slice accounting (jiffy based)
> doesn't work well. CFQ doesn't consider above item 2 & 3.
> 
> FIOPS (Fair IOPS) ioscheduler is trying to fix the gaps. It's IOPS based, so
> only targets for drive without I/O seek. It's quite similar like CFQ, but
> the dispatch decision is made according to IOPS instead of slice.
> 
> The algorithm is simple. Drive has a service tree, and each task lives in
> the tree. The key into the tree is called vios (virtual I/O). Every request
> has vios, which is calculated according to its ioprio, request size and so
> on. Task's vios is the sum of vios of all requests it dispatches. FIOPS
> always selects task with minimum vios in the service tree and let the task
> dispatch request. The dispatched request's vios is then added to the task's
> vios and the task is repositioned in the sevice tree.
> 
> The series are orgnized as:
> Patch 1: separate CFQ's io context management code. FIOPS will use it too.
> Patch 2: The core FIOPS.
> Patch 3: request read/write vios scale. This demontrates how the vios scale.
> 
> To make the code simple for easy view, some scale code isn't included here,
> some not implementated yet.
> 
> TODO:
> 1. ioprio support (have patch already)
> 2. request size vios scale
> 3. cgroup support
> 4. tracing support
> 5. automatically select default iosched according to QUEUE_FLAG_NONROT.
> 
> Comments and suggestions are welcome!

Benchmark results?

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

  parent reply	other threads:[~2012-01-04  7:19 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-01-04  6:53 [RFC 0/3]block: An IOPS based ioscheduler Shaohua Li
2012-01-04  6:53 ` [RFC 1/3]block: seperate CFQ io context management code Shaohua Li
2012-01-04  8:19   ` Namhyung Kim
2012-01-04  6:53 ` [RFC 2/3]block: FIOPS ioscheduler core Shaohua Li
2012-01-06  6:05   ` Namjae Jeon
2012-01-07  1:06   ` Zhu Yanhai
2012-01-04  6:53 ` [RFC 3/3]block: fiops read/write request scale Shaohua Li
2012-01-04  7:19 ` Dave Chinner [this message]
2012-01-05  6:50   ` [RFC 0/3]block: An IOPS based ioscheduler Shaohua Li
2012-01-06  5:12     ` Shaohua Li
2012-01-06  9:10       ` Namhyung Kim
2012-01-06 14:37       ` Jan Kara
2012-01-09  1:26         ` Shaohua Li
2012-01-15 22:32           ` Vivek Goyal
2012-01-08 22:16       ` Dave Chinner
2012-01-09  1:09         ` Shaohua Li
2012-01-15 22:45           ` Vivek Goyal
2012-01-16  4:36             ` Shaohua Li
2012-01-16  7:11               ` Vivek Goyal
2012-01-16  7:55                 ` Shaohua Li
2012-01-16  8:29                   ` Vivek Goyal
2012-01-17  1:06                     ` Shaohua Li
2012-01-17  9:02                       ` Vivek Goyal
2012-01-18  1:20                         ` Shaohua Li
2012-01-18 13:04                           ` Vivek Goyal
2012-01-19  1:21                             ` Shaohua Li
2012-01-15 22:28       ` Vivek Goyal
2012-01-06  9:41 ` Zhu Yanhai
2012-01-15 22:24 ` Vivek Goyal

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