On Mon, Dec 16, 2024 at 8:07 PM Ferry Meng <mengferry@xxxxxxxxxxxxxxxxx> wrote: > > > On 12/16/24 3:38 PM, Jason Wang wrote: > > On Mon, Dec 16, 2024 at 10:01 AM Ferry Meng <mengferry@xxxxxxxxxxxxxxxxx> wrote: > >> > >> On 12/3/24 8:14 PM, Ferry Meng wrote: > >>> We seek to develop a more flexible way to use virtio-blk and bypass the block > >>> layer logic in order to accomplish certain performance optimizations. As a > >>> result, we referred to the implementation of io_uring passthrough in NVMe > >>> and implemented it in the virtio-blk driver. This patch series adds io_uring > >>> passthrough support for virtio-blk devices, resulting in lower submit latency > >>> and increased flexibility when utilizing virtio-blk. > >>> > >>> To test this patch series, I changed fio's code: > >>> 1. Added virtio-blk support to engines/io_uring.c. > >>> 2. Added virtio-blk support to the t/io_uring.c testing tool. > >>> Link: https://github.com/jdmfr/fio > >>> > >>> Using t/io_uring-vblk, the performance of virtio-blk based on uring-cmd > >>> scales better than block device access. (such as below, Virtio-Blk with QEMU, > >>> 1-depth fio) > >>> (passthru) read: IOPS=17.2k, BW=67.4MiB/s (70.6MB/s) > >>> slat (nsec): min=2907, max=43592, avg=3981.87, stdev=595.10 > >>> clat (usec): min=38, max=285,avg=53.47, stdev= 8.28 > >>> lat (usec): min=44, max=288, avg=57.45, stdev= 8.28 > >>> (block) read: IOPS=15.3k, BW=59.8MiB/s (62.7MB/s) > >>> slat (nsec): min=3408, max=35366, avg=5102.17, stdev=790.79 > >>> clat (usec): min=35, max=343, avg=59.63, stdev=10.26 > >>> lat (usec): min=43, max=349, avg=64.73, stdev=10.21 > >>> > >>> Testing the virtio-blk device with fio using 'engines=io_uring_cmd' > >>> and 'engines=io_uring' also demonstrates improvements in submit latency. > >>> (passthru) taskset -c 0 t/io_uring-vblk -b4096 -d8 -c4 -s4 -p0 -F1 -B0 -O0 -n1 -u1 /dev/vdcc0 > >>> IOPS=189.80K, BW=741MiB/s, IOS/call=4/3 > >>> IOPS=187.68K, BW=733MiB/s, IOS/call=4/3 > >>> (block) taskset -c 0 t/io_uring-vblk -b4096 -d8 -c4 -s4 -p0 -F1 -B0 -O0 -n1 -u0 /dev/vdc > >>> IOPS=101.51K, BW=396MiB/s, IOS/call=4/3 > >>> IOPS=100.01K, BW=390MiB/s, IOS/call=4/4 > >>> > >>> The performance overhead of submitting IO can be decreased by 25% overall > >>> with this patch series. The implementation primarily references 'nvme io_uring > >>> passthrough', supporting io_uring_cmd through a separate character interface > >>> (temporarily named /dev/vdXc0). Since this is an early version, many > >>> details need to be taken into account and redesigned, like: > >>> ● Currently, it only considers READ/WRITE scenarios, some more complex operations > >>> not included like discard or zone ops.(Normal sqe64 is sufficient, in my opinion; > >>> following upgrades, sqe128 and cqe32 might not be needed). > >>> ● ...... > >>> > >>> I would appreciate any useful recommendations. > >>> > >>> Ferry Meng (3): > >>> virtio-blk: add virtio-blk chardev support. > >>> virtio-blk: add uring_cmd support for I/O passthru on chardev. > >>> virtio-blk: add uring_cmd iopoll support. > >>> > >>> drivers/block/virtio_blk.c | 325 +++++++++++++++++++++++++++++++- > >>> include/uapi/linux/virtio_blk.h | 16 ++ > >>> 2 files changed, 336 insertions(+), 5 deletions(-) > >> Hi, Micheal & Jason : > >> > >> What about yours' opinion? As virtio-blk maintainer. Looking forward to > >> your reply. > >> > >> Thanks > > If I understand this correctly, this proposal wants to make io_uring a > > transport of the virito-blk command. So the application doesn't need > > to worry about compatibility etc. This seems to be fine. > > > > But I wonder what's the security consideration, for example do we > > allow all virtio-blk commands to be passthroughs and why. > > About 'security consideration', the generic char-dev belongs to root, so > only root can use this passthrough path. This seems like a restriction. A lot of applications want to be run without privilege to be safe. > > On the other hand, to what I know, virtio-blk commands are all related > to 'I/O operations', so we can support all those opcodes with bypassing > vfs&block layer (if we want). I just realized the most basic read/write > in this RFC patch series, others will be considered later. > > > Thanks > > > Thanks
