linux-ext4 - Re: Discussion: is it time to remove dioread

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Message-Id: <20200114233054.890D7A4040@d06av23.portsmouth.uk.ibm.com>
Date:   Wed, 15 Jan 2020 05:00:53 +0530
From:   Ritesh Harjani <riteshh@...ux.ibm.com>
To:     "Theodore Y. Ts'o" <tytso@....edu>, Jan Kara <jack@...e.cz>
Cc:     Xiaoguang Wang <xiaoguang.wang@...ux.alibaba.com>,
        Ext4 Developers List <linux-ext4@...r.kernel.org>,
        joseph.qi@...ux.alibaba.com, Liu Bo <bo.liu@...ux.alibaba.com>
Subject: Re: Discussion: is it time to remove dioread_nolock?



On 1/9/20 10:08 PM, Theodore Y. Ts'o wrote:
> On Thu, Jan 09, 2020 at 02:51:42PM +0530, Ritesh Harjani wrote:
>>> Dbench was slightly impacted; I didn't see any real differences with
>>> compilebench or postmark.  dioread_nolock did improve fio with
>>> sequential reads; which is interesting, since I would have expected
>>
>> IIUC, this Seq. read numbers are with --direct=1 & bs=2MB & ioengine=libaio,
>> correct?
>> So essentially it will do a DIO AIO sequential read.
> 
> Correct.

I too collected some performance numbers on my x86 box with
--direct=1, bs=4K/1M & ioengine=libaio, with default opt v/s 
dioread_nolock opt on latest ext4 git tree.

I found the delta to be within +/- 6% in all of the runs which includes, 
seq read, mixed rw & mixed randrw.

-ritesh