[Cc: virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx, "Michael S. Tsirkin" <mst@xxxxxxxxxx>, Jason Wang <jasowang@xxxxxxxxxx>] It'd be nice to have an ACK for this from the virtio maintainers. Thanks, Miklos On Wed, Aug 21, 2019 at 7:38 PM Vivek Goyal <vgoyal@xxxxxxxxxx> wrote: > > Hi, > > Here are the V3 patches for virtio-fs filesystem. This time I have > broken the patch series in two parts. This is first part which does > not contain DAX support. Second patch series will contain the patches > for DAX support. > > I have also dropped RFC tag from first patch series as we believe its > in good enough shape that it should get a consideration for inclusion > upstream. > > These patches apply on top of 5.3-rc5 kernel and are also available > here. > > https://github.com/rhvgoyal/linux/commits/vivek-5.3-aug-21-2019 > > Patches for V1 and V2 were posted here. > > https://lwn.net/ml/linux-fsdevel/20181210171318.16998-1-vgoyal@xxxxxxxxxx/ > http://lkml.iu.edu/hypermail/linux/kernel/1905.1/07232.html > > More information about the project can be found here. > > https://virtio-fs.gitlab.io > > Changes from V2 > =============== > - Various bug fixes and performance improvements. > > HOWTO > ====== > We have put instructions on how to use it here. > > https://virtio-fs.gitlab.io/ > > Some Performance Numbers > ======================== > I have basically run bunch of fio jobs to get a sense of speed of > various operations. I wrote a simple wrapper script to run fio jobs > 3 times and take their average and report it. These scripts are available > here. > > https://github.com/rhvgoyal/virtiofs-tests > > I set up a directory on ramfs on host and exported that directory inside > guest using virtio-9p and virtio-fs and ran tests inside guests. Ran > tests with cache=none both for virtio-9p and virtio-fs so that no caching > happens in guest. For virtio-fs, I ran an additional set of tests with > dax enabled. Dax is not part of first patch series but I included > results here because dax seems to get the maximum performance advantage > and its shows the real potential of virtio-fs. > > Test Setup > ----------- > - A fedora 28 host with 32G RAM, 2 sockets (6 cores per socket, 2 > threads per core) > > - Using ramfs on host as backing store. 4 fio files of 2G each. > > - Created a VM with 16 VCPUS and 8GB memory. An 8GB cache window (for dax > mmap). > > Test Results > ------------ > - Results in three configurations have been reported. 9p (cache=none), > virtio-fs (cache=none) and virtio-fs (cache=none + dax). > > There are other caching modes as well but to me cache=none seemed most > interesting for now because it does not cache anything in guest > and provides strong coherence. Other modes which provide less strong > coherence and hence are faster are yet to be benchmarked. > > - Three fio ioengines psync, libaio and mmap have been used. > > - I/O Workload of randread, radwrite, seqread and seqwrite have been run. > > - Each file size is 2G. Block size 4K. iodepth=16 > > - "multi" means same operation was done with 4 jobs and each job is > operating on a file of size 2G. > > - Some results are "0 (KiB/s)". That means that particular operation is > not supported in that configuration. > > NAME I/O Operation BW(Read/Write) > > 9p-cache-none seqread-psync 27(MiB/s) > virtiofs-cache-none seqread-psync 35(MiB/s) > virtiofs-dax-cache-none seqread-psync 245(MiB/s) > > 9p-cache-none seqread-psync-multi 117(MiB/s) > virtiofs-cache-none seqread-psync-multi 162(MiB/s) > virtiofs-dax-cache-none seqread-psync-multi 894(MiB/s) > > 9p-cache-none seqread-mmap 24(MiB/s) > virtiofs-cache-none seqread-mmap 0(KiB/s) > virtiofs-dax-cache-none seqread-mmap 168(MiB/s) > > 9p-cache-none seqread-mmap-multi 115(MiB/s) > virtiofs-cache-none seqread-mmap-multi 0(KiB/s) > virtiofs-dax-cache-none seqread-mmap-multi 614(MiB/s) > > 9p-cache-none seqread-libaio 26(MiB/s) > virtiofs-cache-none seqread-libaio 139(MiB/s) > virtiofs-dax-cache-none seqread-libaio 160(MiB/s) > > 9p-cache-none seqread-libaio-multi 129(MiB/s) > virtiofs-cache-none seqread-libaio-multi 142(MiB/s) > virtiofs-dax-cache-none seqread-libaio-multi 577(MiB/s) > > 9p-cache-none randread-psync 29(MiB/s) > virtiofs-cache-none randread-psync 34(MiB/s) > virtiofs-dax-cache-none randread-psync 256(MiB/s) > > 9p-cache-none randread-psync-multi 139(MiB/s) > virtiofs-cache-none randread-psync-multi 153(MiB/s) > virtiofs-dax-cache-none randread-psync-multi 245(MiB/s) > > 9p-cache-none randread-mmap 22(MiB/s) > virtiofs-cache-none randread-mmap 0(KiB/s) > virtiofs-dax-cache-none randread-mmap 162(MiB/s) > > 9p-cache-none randread-mmap-multi 111(MiB/s) > virtiofs-cache-none randread-mmap-multi 0(KiB/s) > virtiofs-dax-cache-none randread-mmap-multi 215(MiB/s) > > 9p-cache-none randread-libaio 26(MiB/s) > virtiofs-cache-none randread-libaio 135(MiB/s) > virtiofs-dax-cache-none randread-libaio 157(MiB/s) > > 9p-cache-none randread-libaio-multi 133(MiB/s) > virtiofs-cache-none randread-libaio-multi 245(MiB/s) > virtiofs-dax-cache-none randread-libaio-multi 163(MiB/s) > > 9p-cache-none seqwrite-psync 28(MiB/s) > virtiofs-cache-none seqwrite-psync 34(MiB/s) > virtiofs-dax-cache-none seqwrite-psync 203(MiB/s) > > 9p-cache-none seqwrite-psync-multi 128(MiB/s) > virtiofs-cache-none seqwrite-psync-multi 155(MiB/s) > virtiofs-dax-cache-none seqwrite-psync-multi 717(MiB/s) > > 9p-cache-none seqwrite-mmap 0(KiB/s) > virtiofs-cache-none seqwrite-mmap 0(KiB/s) > virtiofs-dax-cache-none seqwrite-mmap 165(MiB/s) > > 9p-cache-none seqwrite-mmap-multi 0(KiB/s) > virtiofs-cache-none seqwrite-mmap-multi 0(KiB/s) > virtiofs-dax-cache-none seqwrite-mmap-multi 511(MiB/s) > > 9p-cache-none seqwrite-libaio 27(MiB/s) > virtiofs-cache-none seqwrite-libaio 128(MiB/s) > virtiofs-dax-cache-none seqwrite-libaio 141(MiB/s) > > 9p-cache-none seqwrite-libaio-multi 119(MiB/s) > virtiofs-cache-none seqwrite-libaio-multi 242(MiB/s) > virtiofs-dax-cache-none seqwrite-libaio-multi 505(MiB/s) > > 9p-cache-none randwrite-psync 27(MiB/s) > virtiofs-cache-none randwrite-psync 34(MiB/s) > virtiofs-dax-cache-none randwrite-psync 189(MiB/s) > > 9p-cache-none randwrite-psync-multi 137(MiB/s) > virtiofs-cache-none randwrite-psync-multi 150(MiB/s) > virtiofs-dax-cache-none randwrite-psync-multi 233(MiB/s) > > 9p-cache-none randwrite-mmap 0(KiB/s) > virtiofs-cache-none randwrite-mmap 0(KiB/s) > virtiofs-dax-cache-none randwrite-mmap 120(MiB/s) > > 9p-cache-none randwrite-mmap-multi 0(KiB/s) > virtiofs-cache-none randwrite-mmap-multi 0(KiB/s) > virtiofs-dax-cache-none randwrite-mmap-multi 200(MiB/s) > > 9p-cache-none randwrite-libaio 25(MiB/s) > virtiofs-cache-none randwrite-libaio 124(MiB/s) > virtiofs-dax-cache-none randwrite-libaio 131(MiB/s) > > 9p-cache-none randwrite-libaio-multi 125(MiB/s) > virtiofs-cache-none randwrite-libaio-multi 241(MiB/s) > virtiofs-dax-cache-none randwrite-libaio-multi 163(MiB/s) > > Conclusions > =========== > - In general virtio-fs seems faster than virtio-9p. Using dax makes it > really interesting. > > Note: > Right now dax window is 8G and max fio file size is 8G as well (4 > files of 2G each). That means everything fits into dax window and no > reclaim is needed. Dax window reclaim logic is slower and if file > size is bigger than dax window size, performance slows down. > > Description from previous postings > ================================== > > Design Overview > =============== > With the goal of designing something with better performance and local file > system semantics, a bunch of ideas were proposed. > > - Use fuse protocol (instead of 9p) for communication between guest > and host. Guest kernel will be fuse client and a fuse server will > run on host to serve the requests. > > - For data access inside guest, mmap portion of file in QEMU address > space and guest accesses this memory using dax. That way guest page > cache is bypassed and there is only one copy of data (on host). This > will also enable mmap(MAP_SHARED) between guests. > > - For metadata coherency, there is a shared memory region which contains > version number associated with metadata and any guest changing metadata > updates version number and other guests refresh metadata on next > access. This is yet to be implemented. > > How virtio-fs differs from existing approaches > ============================================== > The unique idea behind virtio-fs is to take advantage of the co-location > of the virtual machine and hypervisor to avoid communication (vmexits). > > DAX allows file contents to be accessed without communication with the > hypervisor. The shared memory region for metadata avoids communication in > the common case where metadata is unchanged. > > By replacing expensive communication with cheaper shared memory accesses, > we expect to achieve better performance than approaches based on network > file system protocols. In addition, this also makes it easier to achieve > local file system semantics (coherency). > > These techniques are not applicable to network file system protocols since > the communications channel is bypassed by taking advantage of shared memory > on a local machine. This is why we decided to build virtio-fs rather than > focus on 9P or NFS. > > Caching Modes > ============= > Like virtio-9p, different caching modes are supported which determine the > coherency level as well. The “cache=FOO” and “writeback” options control the > level of coherence between the guest and host filesystems. > > - cache=none > metadata, data and pathname lookup are not cached in guest. They are always > fetched from host and any changes are immediately pushed to host. > > - cache=always > metadata, data and pathname lookup are cached in guest and never expire. > > - cache=auto > metadata and pathname lookup cache expires after a configured amount of time > (default is 1 second). Data is cached while the file is open (close to open > consistency). > > - writeback/no_writeback > These options control the writeback strategy. If writeback is disabled, > then normal writes will immediately be synchronized with the host fs. If > writeback is enabled, then writes may be cached in the guest until the file > is closed or an fsync(2) performed. This option has no effect on mmap-ed > writes or writes going through the DAX mechanism. > > Thanks > Vivek > > Miklos Szeredi (2): > fuse: delete dentry if timeout is zero > fuse: Use default_file_splice_read for direct IO > > Stefan Hajnoczi (6): > fuse: export fuse_end_request() > fuse: export fuse_len_args() > fuse: export fuse_get_unique() > fuse: extract fuse_fill_super_common() > fuse: add fuse_iqueue_ops callbacks > virtio_fs: add skeleton virtio_fs.ko module > > Vivek Goyal (5): > fuse: Export fuse_send_init_request() > Export fuse_dequeue_forget() function > fuse: Separate fuse device allocation and installation in fuse_conn > virtio-fs: Do not provide abort interface in fusectl > init/do_mounts.c: add virtio_fs root fs support > > fs/fuse/Kconfig | 11 + > fs/fuse/Makefile | 1 + > fs/fuse/control.c | 4 +- > fs/fuse/cuse.c | 4 +- > fs/fuse/dev.c | 89 ++- > fs/fuse/dir.c | 26 +- > fs/fuse/file.c | 15 +- > fs/fuse/fuse_i.h | 120 +++- > fs/fuse/inode.c | 203 +++--- > fs/fuse/virtio_fs.c | 1061 +++++++++++++++++++++++++++++++ > fs/splice.c | 3 +- > include/linux/fs.h | 2 + > include/uapi/linux/virtio_fs.h | 41 ++ > include/uapi/linux/virtio_ids.h | 1 + > init/do_mounts.c | 10 + > 15 files changed, 1462 insertions(+), 129 deletions(-) > create mode 100644 fs/fuse/virtio_fs.c > create mode 100644 include/uapi/linux/virtio_fs.h > > -- > 2.20.1 >
