On Tue, Sep 03, 2019 at 10:05:02AM +0200, Miklos Szeredi wrote: > [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 Can the patches themselves be posted to the relevant list(s) please? If possible, please also include "v3" in all patches so they are easier to find. I poked at https://lwn.net/ml/linux-kernel/20190821173742.24574-1-vgoyal@xxxxxxxxxx/ specifically https://lwn.net/ml/linux-kernel/20190821173742.24574-12-vgoyal@xxxxxxxxxx/ and things like: + /* TODO lock */ give me pause. Cleanup generally seems broken to me - what pauses the FS What about the rest of TODOs in that file? use of usleep is hacky - can't we do better e.g. with a completion? Some typos - e.g. "reuests". > > 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 Don't the new files need a MAINTAINERS entry? I think we want virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx to be copied. > > > > -- > > 2.20.1 > >
