RE: [RFC PATCH 0/2] blk-mq I/O scheduling fixes

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Sir,

The HDD is hardware Raid 5 with 530-8i raid card.
I tried 1m seq write with numjobs=1, the data similar as kernel 3.10.0, whatever mq-deadline or BFQ elevator.
If you need detail testing data with numjobs=1, I can do it. Or any info you need, such as two process with 1 thread.

Thank you.

BestRegards,
SunnyLiu(刘萍)
LenovoNetApp 
北京市海淀区西北旺东路10号院2号楼L3-E1-01
L3-E1-01,Building No.2, Lenovo HQ West No.10 XiBeiWang East Rd.,
Haidian District, Beijing 100094, PRC
Tel: +86 15910622368

-----Original Message-----
From: linux-block-owner@xxxxxxxxxxxxxxx <linux-block-owner@xxxxxxxxxxxxxxx> On Behalf Of Damien Le Moal
Sent: 2019年9月19日 20:45
To: Liu, Sunny <ping.liu@xxxxxxxxxxxxxxxx>; Hannes Reinecke <hare@xxxxxxx>; Jens Axboe <axboe@xxxxxxxxx>
Cc: linux-scsi@xxxxxxxxxxxxxxx; Martin K. Petersen <martin.petersen@xxxxxxxxxx>; James Bottomley <james.bottomley@xxxxxxxxxxxxxxxxxxxxx>; Christoph Hellwig <hch@xxxxxx>; linux-block@xxxxxxxxxxxxxxx; Hans Holmberg <Hans.Holmberg@xxxxxxx>
Subject: Re: [RFC PATCH 0/2] blk-mq I/O scheduling fixes

On 2019/09/19 12:59, Liu, Sunny wrote:
> Thank very much for your quickly advice.
> 
> The problem drive is sata HDD 7200rpm in raid 5.

Sorry, I read "SDD" where you had written "HDD" :) Is this a hardware RAID ? Or is this using dm/md raid ?

> If using Fio libaio iodepth=128 numjob=2, the bad performance will be 
> as below in red. But there is no problem with numjob=1. In our 
> solution, *multiple
> threads* should be used.

Your data does not have the numjobs=1 case for kernel 5.2.9. You should run that for comparison with the numjobs=2 case on the same kernel.

> From the testing result, BFQ low-latency had good performance, but it 
> still has problem in 1m seq write.
> 
> The data is come from centos 7.6 (kernel 3.10.0-975) and kernel 5.2.9 
> with BFQ and bcache enabled. No bcache configure.
> 
> Is there any parameter can solve the 1m and upper seq write problem 
> with multiple threads?

Not sure what the problem is here. You could look at a blktrace of each case to see if there is any major difference in the command patterns sent to the disks of your array, in particular command size.

--
Damien Le Moal
Western Digital Research




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