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Subject: Re: [PATCH] virtio_blk: set the default scheduler to none
From:   Li Feng <fengli@smartx.com>
In-Reply-To: <9b963af6-0a3f-4957-9227-43673e70b720@nvidia.com>
Date:   Thu, 7 Dec 2023 15:21:44 +0800
Cc:     Jens Axboe <axboe@kernel.dk>,
        "Michael S. Tsirkin" <mst@redhat.com>,
        Jason Wang <jasowang@redhat.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Stefan Hajnoczi <stefanha@redhat.com>,
        Xuan Zhuo <xuanzhuo@linux.alibaba.com>,
        "open list:BLOCK LAYER" <linux-block@vger.kernel.org>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        "open list:VIRTIO BLOCK AND SCSI DRIVERS" 
        <virtualization@lists.linux.dev>
Content-Transfer-Encoding: quoted-printable
Message-Id: <ADCE81A1-D65A-41C4-A485-66E1B056B1CC@smartx.com>
References: <20231207043118.118158-1-fengli@smartx.com>
 <9b963af6-0a3f-4957-9227-43673e70b720@nvidia.com>
To:     Chaitanya Kulkarni <chaitanyak@nvidia.com>
Precedence: bulk


> On Dec 7, 2023, at 14:53, Chaitanya Kulkarni <chaitanyak@nvidia.com> =
wrote:
>=20
> On 12/6/23 20:31, Li Feng wrote:
>> virtio-blk is generally used in cloud computing scenarios, where the
>> performance of virtual disks is very important. The mq-deadline =
scheduler
>> has a big performance drop compared to none with single queue. In my =
tests,
>> mq-deadline 4k readread iops were 270k compared to 450k for none. So =
here
>> the default scheduler of virtio-blk is set to "none".
>>=20
>> Signed-off-by: Li Feng <fengli@smartx.com>
>> ---
>>=20
>=20
> This patch looks good to me, however I'd update the commit log and add
> performance numbers for the non-mq case also, just in-case to show =
that we
> are not breaking non-mq setup.
>=20
> Being said that, in case we want to be future proof, we can also think =
of
> adding a module param so if someone comes with a scenario where =
NO_SCHED is
> not providing the performance then they can just use the module =
parameter
> instead of again editing the code, irrespective of that :-
>=20
> Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
>=20
> -ck

Hi ck,

What I put above(450k vs 270k) is the data of single queue(non-mq). I =
think
we don=E2=80=99t need to add module parameters because the scheduler can =
be modified
through sysfs.

Thanks.

>=20
>=20