linux-kernel - Re: [PATCH] virtio_blk: set the default scheduler to none

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <ZXKDFdzXN4xQAuBm@kbusch-mbp>
Date:   Thu, 7 Dec 2023 19:44:37 -0700
From:   Keith Busch <kbusch@...nel.org>
To:     Ming Lei <ming.lei@...hat.com>
Cc:     Li Feng <fengli@...rtx.com>, Jens Axboe <axboe@...nel.dk>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Stefan Hajnoczi <stefanha@...hat.com>,
        Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
        "open list:BLOCK LAYER" <linux-block@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        "open list:VIRTIO BLOCK AND SCSI DRIVERS" 
        <virtualization@...ts.linux.dev>
Subject: Re: [PATCH] virtio_blk: set the default scheduler to none

On Fri, Dec 08, 2023 at 10:00:36AM +0800, Ming Lei wrote:
> On Thu, Dec 07, 2023 at 12:31:05PM +0800, 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".
> 
> The test result shows you may not test HDD. backing of virtio-blk.
> 
> none can lose IO merge capability more or less, so probably sequential IO perf
> drops in case of HDD backing.

More of a curiosity, as I don't immediately even have an HDD to test
with! Isn't it more useful for the host providing the backing HDD use an
appropriate IO scheduler? virtio-blk has similiarities with a stacking
block driver, and we usually don't need to stack IO schedulers.