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Subject: Re: [Qemu-devel] [RFC] About 9pfs support "O_DIRECT + aio"?
To:     jiangyiwen <jiangyiwen@huawei.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Eric Van Hensbergen <ericvh@gmail.com>,
        Ron Minnich <rminnich@sandia.gov>,
        Latchesar Ionkov <lucho@ionkov.net>,
        Greg Kurz <groug@kaod.org>, aneesh.kumar@linux.vnet.ibm.com
Cc:     v9fs-developer@lists.sourceforge.net, linux-kernel@vger.kernel.org,
        qemu-devel@nongnu.org
References: <5ABDFB24.1080207@huawei.com>
From:   Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <41088460-11f1-1ec7-2bfa-1ebdf675dc17@redhat.com>
Date:   Mon, 2 Apr 2018 04:45:36 +0200
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On 30/03/2018 10:53, jiangyiwen wrote:
> Currently, I found virtio-9p in VirtFS don't support "O_DIRECT + aio"
> mode, both v9fs and qemu. So when user use "O_DIRECT + aio" mode and
> increase iodepths, they can't get higher IOPS.
> 
> I want to know why v9fs don't implement this mode? And I will try to
> implement this mode from now on.

Can you explain?  I think 9p has support for direct I/O in Linux.  See
v9fs_direct_IO in fs/9p/vfs_addr.c.

Paolo