Messages in this thread | | | Subject | Re: [patch v2 0/8]block: An IOPS based ioscheduler | From | Shaohua Li <> | Date | Tue, 31 Jan 2012 08:50:40 +0800 |
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On Mon, 2012-01-30 at 10:30 -0500, Vivek Goyal wrote: > On Mon, Jan 30, 2012 at 03:02:13PM +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. > > Hi Shaohua, > > Last time we agreed that you will try to extend CFQ iops mode to take care > of this case. I was wondering that if that idea is out of the window? I felt there is complexity to do the merge and mess code even with wrapping some functions as you suggested. Another thing is I want to avoid complexity of CFQ, for example allocating queue and sharing it between tasks. cfq_set_request is one source that queue_lock gets contented, making the code simple can avoid such contention.
> Also what's the real workload where this is going to benefit us. I had > struggled to run something which drove constantly deep queue depths to > get the fairness without idling. To be honest, I don't have real workload. Our test environment runs some micro benchmarks, which has some problems. I thought we all agreed CFQ has some limitations. Hoping somebody having real workload can have a look.
Thanks, Shaohua
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