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Subject: Re: [PATCH 0/1] vhost: add vhost_blk driver
To:     Vitaly Mayatskih <v.mayatskih@gmail.com>
Cc:     "Michael S . Tsirkin" <mst@redhat.com>,
        Paolo Bonzini <pbonzini@redhat.com>, kvm@vger.kernel.org,
        virtualization@lists.linux-foundation.org,
        linux-kernel@vger.kernel.org, stefanha@redhat.com
References: <20181102182123.29420-1-v.mayatskih@gmail.com>
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 <CAGF4SLg6+nt+zV4haXys4Wz2dWPDyx7xHXuA+h01NcQ94j0E1A@mail.gmail.com>
From:   Jason Wang <jasowang@redhat.com>
Message-ID: <57eefa62-7e66-786d-441c-5dd6b0d451a5@redhat.com>
Date:   Tue, 6 Nov 2018 10:45:08 +0800
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On 2018/11/5 上午11:23, Vitaly Mayatskih wrote:
> On Sun, Nov 4, 2018 at 10:00 PM Jason Wang <jasowang@redhat.com> wrote:
>
>>> # fio num-jobs
>>> # A: bare metal over block
>>> # B: bare metal over file
>>> # C: virtio-blk over block
>>> # D: virtio-blk over file
>>> # E: vhost-blk bio over block
>>> # F: vhost-blk kiocb over block
>>> # G: vhost-blk kiocb over file
>>> #
>>> #  A     B     C    D    E     F     G
>>> 16 1480k 1506k 101k 102k 1346k 1202k 566k
>> Hi:
>>
>> Thanks for the patches.
>>
>> This is not the first attempt for having vhost-blk:
>>
>> - Badari's version: https://lwn.net/Articles/379864/
>>
>> - Asias' version: https://lwn.net/Articles/519880/
>>
>> It's better to describe the differences (kiocb vs bio? performance?).
>> E.g if my memory is correct, Asias said it doesn't give much improvement
>> compared with userspace qemu.
>>
>> And what's more important, I believe we tend to use virtio-scsi nowdays.
>> So what's the advantages of vhost-blk over vhost-scsi?
> Hi,
>
> Yes, I saw both. Frankly, my implementation is not that different,
> because the whole thing has only twice more LOC that vhost/test.c.
>
> I posted my numbers (see in quoted text above the 16 queues case),
> IOPS goes from ~100k to 1.2M and almost reaches the physical
> limitation of the backend.
>
> submit_bio() is a bit faster, but can't be used for disk images placed
> on a file system. I have that submit_bio implementation too.
>
> Storage industry is shifting away from SCSI, which has a scaling
> problem.


Know little about storage. For scaling, do you mean SCSI protocol 
itself? If not, it's probably not a real issue for virtio-scsi itself.


>   I can compare vhost-scsi vs vhost-blk if you are curious.


It would be very helpful to see the performance comparison.


Thanks


> Thanks!