linux-kernel - [RFC v2 0/5] virtiofs: map buffer out of virtqueue lock

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Message-ID: <20250221170626.261687-1-eperezma@redhat.com>
Date: Fri, 21 Feb 2025 18:06:21 +0100
From: Eugenio Pérez <eperezma@...hat.com>
To: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
	Stefan Hajnoczi <stefanha@...hat.com>,
	Hanna Reitz <hreitz@...hat.com>,
	linux-kernel@...r.kernel.org,
	German Maglione <gmaglione@...hat.com>,
	virtualization@...ts.linux.dev,
	Stefano Garzarella <sgarzare@...hat.com>,
	yama@...hat.com,
	Vivek Goyal <vgoyal@...hat.com>,
	Miklos Szeredi <miklos@...redi.hu>,
	mst@...hat.com,
	Jason Wang <jasowang@...hat.com>
Subject: [RFC v2 0/5] virtiofs: map buffer out of virtqueue lock

This is useful for some setups like swiotlb or VDUSE where the DMA
operations are expensive and/or need to be performed with a write lock.

After applying these patches, fio read test goes from 1124MiB/s to
1263.14MiB/s.

v2:
* Follow current add_premapped virtio API
* Disable notification more aggressive too.

---
Sending this series to obtain feedback if this is the right way to go &
to profile it properly.

TODO: Profile multiqueue.
TODO: Handling errors.
TODO: Do the same for hiprio queue.
TODO: Can we batch maps? virtiofs always sends many buffers.

Eugenio Pérez (5):
  vduse: add virtio_fs to allowed dev id
  virtiofs: Move stack sg to fuse_req
  virtio_ring: add api for premapped out and in buffer chain
  virtiofs: perform DMA operations out of the spinlock
  virtiofs: Disable notifications more aggresively

 drivers/vdpa/vdpa_user/vduse_dev.c |  1 +
 drivers/virtio/virtio_ring.c       | 35 ++++++++++++
 fs/fuse/fuse_i.h                   |  7 +++
 fs/fuse/virtio_fs.c                | 85 +++++++++++++++++++++---------
 include/linux/virtio.h             |  7 +++
 5 files changed, 110 insertions(+), 25 deletions(-)

-- 
2.48.1