Re: [PATCH v5 0/7] vhost-user-blk: fix the migration issue and enhance qtests

[Dima Stepanov <dimastep@yandex-team.ru>]

On Tue, Sep 29, 2020 at 03:13:09AM -0400, Michael S. Tsirkin wrote:
> On Sun, Sep 27, 2020 at 09:48:28AM +0300, Dima Stepanov wrote:
> > On Thu, Sep 24, 2020 at 07:26:14AM -0400, Michael S. Tsirkin wrote:
> > > On Fri, Sep 11, 2020 at 11:39:42AM +0300, Dima Stepanov wrote:
> > > > v4 -> v5:
> > > >   - vhost: check queue state in the vhost_dev_set_log routine
> > > >     tests/qtest/vhost-user-test: prepare the tests for adding new
> > > >     dev class
> > > >     tests/qtest/vhost-user-test: add support for the
> > > >     vhost-user-blk device
> > > >     tests/qtest/vhost-user-test: add migrate_reconnect test
> > > >     Reviewed-by: Raphael Norwitz
> > > >   - Update qtest, by merging vhost-user-blk "if" case with the
> > > >     virtio-blk case.
> > > 
> > > I dropped patches 3-7 since they were stalling on some systems.
> > > Pls work with Peter Maydell (cc'd) to figure it out.
> > Thanks!
> > 
> > Peter, can you share any details for the stalling errors with me?
> 
> I can say for sure that even on x86/linux the affected tests take
> much longer to run with these applied.
> I'd suggest making sure there are no timeouts involved in the good case ....
Could you help me to reproduce it? Because on my system i see only 10+ seconds
increase for the qos-test set to pass (both x86_64 and i386). So on the
current master i'm running it like:
  - ./configure  --target-list="x86_64-softmmu i386-softmmu"
  - with no patch set:
    time QTEST_QEMU_BINARY=./build/x86_64-softmmu/qemu-system-x86_64 ./build/tests/qtest/qos-test
    real    0m6.394s
    user    0m3.643s
    sys     0m3.477s
  - without patch 7 (where i include vhost-user-net tests also):
    real    0m9.955s
    user    0m4.133s
    sys     0m4.397s
  - full patch set:
    real    0m17.263s
    user    0m4.530s
    sys     0m4.802s
For i386 target i see pretty the same numbers:
  time QTEST_QEMU_BINARY=./build/i386-softmmu/qemu-system-i386 ./build/tests/qtest/qos-test
  real    0m17.386s
  user    0m4.503s
  sys     0m4.911s
So it looks like that i'm missing some step to reproduce an issue.

And if i run the exact test it takes ~2-3s to pass:
  $ time QTEST_QEMU_BINARY=./build/x86_64-softmmu/qemu-system-x86_64 ./build/tests/qtest/qos-test -p /x86_64/pc/i440FX-pcihost/pci-bus-pc/pci-bus/vhost-user-blk-pci/vhost-user-blk/vhost-user-blk-tests/reconnect
  /x86_64/pc/i440FX-pcihost/pci-bus-pc/pci-bus/vhost-user-blk-pci/vhost-user-blk/vhost-user-blk-tests/reconnect: OK
  real    0m2.253s
  user    0m0.118s
  sys     0m0.104s
And same numbers for i386.

> 
> > > 
> > > 
> > > > v3 -> v4:
> > > >   - vhost: recheck dev state in the vhost_migration_log routine
> > > >     Reviewed-by: Raphael Norwitz
> > > >   - vhost: check queue state in the vhost_dev_set_log routine
> > > >     Use "continue" instead of "break" to handle non-initialized
> > > >     virtqueue case.
> > > > 
> > > > v2 -> v3:
> > > >   - update commit message for the 
> > > >     "vhost: recheck dev state in the vhost_migration_log routine" commit
> > > >   - rename "started" field of the VhostUserBlk structure to
> > > >     "started_vu", so there will be no confustion with the VHOST started
> > > >     field
> > > >   - update vhost-user-test.c to always initialize nq local variable
> > > >     (spotted by patchew)
> > > > 
> > > > v1 -> v2:
> > > >   - add comments to connected/started fields in the header file
> > > >   - move the "s->started" logic from the vhost_user_blk_disconnect
> > > >     routine to the vhost_user_blk_stop routine
> > > > 
> > > > Reference e-mail threads:
> > > >   - https://lists.gnu.org/archive/html/qemu-devel/2020-05/msg01509.html
> > > >   - https://lists.gnu.org/archive/html/qemu-devel/2020-05/msg05241.html
> > > > 
> > > > If vhost-user daemon is used as a backend for the vhost device, then we
> > > > should consider a possibility of disconnect at any moment. There was a general
> > > > question here: should we consider it as an error or okay state for the vhost-user
> > > > devices during migration process?
> > > > I think the disconnect event for the vhost-user devices should not break the
> > > > migration process, because:
> > > >   - the device will be in the stopped state, so it will not be changed
> > > >     during migration
> > > >   - if reconnect will be made the migration log will be reinitialized as
> > > >     part of reconnect/init process:
> > > >     #0  vhost_log_global_start (listener=0x563989cf7be0)
> > > >     at hw/virtio/vhost.c:920
> > > >     #1  0x000056398603d8bc in listener_add_address_space (listener=0x563989cf7be0,
> > > >         as=0x563986ea4340 <address_space_memory>)
> > > >     at softmmu/memory.c:2664
> > > >     #2  0x000056398603dd30 in memory_listener_register (listener=0x563989cf7be0,
> > > >         as=0x563986ea4340 <address_space_memory>)
> > > >     at softmmu/memory.c:2740
> > > >     #3  0x0000563985fd6956 in vhost_dev_init (hdev=0x563989cf7bd8,
> > > >         opaque=0x563989cf7e30, backend_type=VHOST_BACKEND_TYPE_USER,
> > > >         busyloop_timeout=0)
> > > >     at hw/virtio/vhost.c:1385
> > > >     #4  0x0000563985f7d0b8 in vhost_user_blk_connect (dev=0x563989cf7990)
> > > >     at hw/block/vhost-user-blk.c:315
> > > >     #5  0x0000563985f7d3f6 in vhost_user_blk_event (opaque=0x563989cf7990,
> > > >         event=CHR_EVENT_OPENED)
> > > >     at hw/block/vhost-user-blk.c:379
> > > > The first patch in the patchset fixes this issue by setting vhost device to the
> > > > stopped state in the disconnect handler and check it the vhost_migration_log()
> > > > routine before returning from the function.
> > > > qtest framework was updated to test vhost-user-blk functionality. The
> > > > vhost-user-blk/vhost-user-blk-tests/migrate_reconnect test was added to reproduce
> > > > the original issue found.
> > > > 
> > > > Dima Stepanov (7):
> > > >   vhost: recheck dev state in the vhost_migration_log routine
> > > >   vhost: check queue state in the vhost_dev_set_log routine
> > > >   tests/qtest/vhost-user-test: prepare the tests for adding new dev
> > > >     class
> > > >   tests/qtest/libqos/virtio-blk: add support for vhost-user-blk
> > > >   tests/qtest/vhost-user-test: add support for the vhost-user-blk device
> > > >   tests/qtest/vhost-user-test: add migrate_reconnect test
> > > >   tests/qtest/vhost-user-test: enable the reconnect tests
> > > > 
> > > >  hw/block/vhost-user-blk.c          |  19 ++-
> > > >  hw/virtio/vhost.c                  |  39 ++++-
> > > >  include/hw/virtio/vhost-user-blk.h |  10 ++
> > > >  tests/qtest/libqos/virtio-blk.c    |  14 +-
> > > >  tests/qtest/vhost-user-test.c      | 290 +++++++++++++++++++++++++++++++------
> > > >  5 files changed, 322 insertions(+), 50 deletions(-)
> > > > 
> > > > -- 
> > > > 2.7.4
> > > 
>