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Subject: Re: [RFC] scsi: switch to scsi-mq by default
To:     Bart Van Assche <Bart.VanAssche@wdc.com>,
        "jthumshirn@suse.de" <jthumshirn@suse.de>,
        "martin.petersen@oracle.com" <martin.petersen@oracle.com>
References: <20180703065413.6098-1-jthumshirn@suse.de>
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CC:     "hch@lst.de" <hch@lst.de>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "hare@suse.de" <hare@suse.de>,
        "tom.leiming@gmail.com" <tom.leiming@gmail.com>,
        "linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>,
        chenxiang <chenxiang66@hisilicon.com>,
        Linuxarm <linuxarm@huawei.com>
From:   John Garry <john.garry@huawei.com>
Message-ID: <282521f4-762c-86a5-5ac8-f8cc33b050cc@huawei.com>
Date:   Wed, 4 Jul 2018 09:18:23 +0100
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On 04/07/2018 00:21, Bart Van Assche wrote:
> On Tue, 2018-07-03 at 08:54 +0200, Johannes Thumshirn wrote:
>> It has been more than one year since we tried to change the default
>> from legacy to multi queue in SCSI. Back then we had to retract the
>> change because of performance issues with rotating disks.
>>
>> In the meantime there have been a substantial amount of performance
>> improvements, thus we can re-enable scsi-mq without a significant
>> performance penalty.
>
> Hello Johannes,
>
> Please include references to commits cbe7dfa26eee ("Revert "scsi:
> default to scsi-mq"") and 5c279bd9e406 ("scsi: default to scsi-mq").
> I think it's a good idea to mention that suspend/resume now works
> with scsi-mq.
>
> Bart.

We were seeing performance drops previously for hisi_sas when originally 
enabled by default, but results on 4.18 seem almost identical with and 
without MQ default.

FWIW,

Acked-by: John Garry <john.garry@huawei.com>

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