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List:       qemu-block
Subject:    Re: [ANNOUNCE] libblkio v0.1.0 preview release
From:       Stefan Hajnoczi <stefanha () redhat ! com>
Date:       2021-04-30 16:20:54
Message-ID: YIwuZrw/573HqvUe () stefanha-x1 ! localdomain
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On Thu, Apr 29, 2021 at 04:00:38PM +0100, Richard W.M. Jones wrote:
> On Thu, Apr 29, 2021 at 03:41:29PM +0100, Stefan Hajnoczi wrote:
> > On Thu, Apr 29, 2021 at 03:22:59PM +0100, Richard W.M. Jones wrote:
> > > This is where I get confused about what this library actually does.
> > > It's not just a nicer wrapper around io_uring, but what is it actually
> > > doing?
> > 
> > It's a library for what QEMU calls protocol drivers (POSIX files,
> > userspace NVMe driver, etc). In particular, anything offering
> > multi-queue block I/O fits into libblkio.
> > 
> > It is not intended to replace libnbd or other network storage libraries.
> > libblkio's properties API is synchronous to keep things simple for
> > applications. Attaching to network storage needs to be asynchronous,
> > although the libblkio API could be extended if people want to support
> > network storage.
> 
> I think what confuses me is why is NVMe any different from io_uring?
> ie would this work?
> 
> $ blkio-info --output=json io_uring path=/dev/nvme0

The libblkio io_uring driver can handle /dev/nvme* block devices.

The future userspace NVMe driver mentioned above will be a VFIO PCI
driver, like the block/nvme.c driver in QEMU today. It uses a PCI device
directly, not a /dev/nvme* block device.

Stefan

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