[ovs-dev] [PATCH v9] dpif-netdev: Assign ports to pmds on non-local numa node.

O Mahony, Billy billy.o.mahony at intel.com
Mon Jul 10 10:42:11 UTC 2017



> -----Original Message-----
> From: Stokes, Ian
> Sent: Monday, July 10, 2017 10:41 AM
> To: Ilya Maximets <i.maximets at samsung.com>; O Mahony, Billy
> <billy.o.mahony at intel.com>; dev at openvswitch.org
> Cc: dball at vmare.com
> Subject: RE: [ovs-dev] [PATCH v9] dpif-netdev: Assign ports to pmds on non-
> local numa node.
> 
> > On 08.07.2017 22:09, Stokes, Ian wrote:
> > >> Previously if there is no available (non-isolated) pmd on the numa
> > >> node for a port then the port is not polled at all. This can result
> > >> in a non- operational system until such time as nics are physically
> > >> repositioned. It is preferable to operate with a pmd on the 'wrong'
> > >> numa node albeit with lower performance. Local pmds are still
> > >> chosen
> > when available.
> > >>
> > >> Signed-off-by: Billy O'Mahony <billy.o.mahony at intel.com>
> > >> Signed-off-by: Ilya Maximets <i.maximets at samsung.com>
> > >> Co-authored-by: Ilya Maximets <i.maximets at samsung.com>
> > >> ---
> > >> v9: v8 missed some comments on v7
> > >> v8: Some coding style issues; doc tweak
> > >> v7: Incorporate review comments on docs and implementation
> > >> v6: Change 'port' to 'queue' in a warning msg
> > >> v5: Fix warning msg; Update same in docs
> > >> v4: Fix a checkpatch error
> > >> v3: Fix warning messages not appearing when using multiqueue
> > >> v2: Add details of warning messages into docs
> > >>
> > >>  Documentation/intro/install/dpdk.rst | 21 +++++++++++++++---
> > >>  lib/dpif-netdev.c                    | 41
> > >> +++++++++++++++++++++++++++++++++---
> > >>  2 files changed, 56 insertions(+), 6 deletions(-)
> > >>
> > >> diff --git a/Documentation/intro/install/dpdk.rst
> > >> b/Documentation/intro/install/dpdk.rst
> > >> index e83f852..89775d6 100644
> > >> --- a/Documentation/intro/install/dpdk.rst
> > >> +++ b/Documentation/intro/install/dpdk.rst
> > >> @@ -449,7 +449,7 @@ affinitized accordingly.
> > >>
> > >>    A poll mode driver (pmd) thread handles the I/O of all DPDK
> > interfaces
> > >>    assigned to it. A pmd thread shall poll the ports for incoming
> > >> packets,
> > >> -  switch the packets and send to tx port.  pmd thread is CPU
> > >> bound, and needs
> > >> +  switch the packets and send to tx port.  A pmd thread is CPU
> > >> + bound, and needs
> > >>    to be affinitized to isolated cores for optimum performance.
> > >>
> > >>    By setting a bit in the mask, a pmd thread is created and pinned
> > >> to the @@ -458,8 +458,23 @@ affinitized accordingly.
> > >>        $ ovs-vsctl set Open_vSwitch . other_config:pmd-cpu-mask=0x4
> > >>
> > >>    .. note::
> > >> -    pmd thread on a NUMA node is only created if there is at least one
> > >> DPDK
> > >> -    interface from that NUMA node added to OVS.
> > >> +    A pmd thread on a NUMA node is only created if there is at
> > >> + least one
> > >> DPDK
> > >> +    interface from that NUMA node added to OVS.  A pmd thread is
> > >> + created
> > >> by
> > >> +    default on a core of a NUMA node or when a specified
> > >> + pmd-cpu-mask
> > has
> > >> +    indicated so.  Even though a PMD thread may exist, the thread
> > >> + only
> > >> starts
> > >> +    consuming CPU cycles if there is least one receive queue
> > >> + assigned
> > to
> > >> +    the pmd.
> > >> +
> > >> +  .. note::
> > >> +    On NUMA systems PCI devices are also local to a NUMA node.
> > >> + Unbound
> > >> rx
> > >> +    queues for a PCI device will assigned to a pmd on it's local
> > >> + NUMA
> > >
> > > Minor point but should read 'will be assigned'

[[BO'M]] 
+1

> > >> node if a
> > >> +    non-isolated PMD exists on that NUMA node.  If not, the queue
> > >> + will
> > be
> > >> +    assigned to a non-isolated pmd on a remote NUMA node.  This
> > >> + will
> > >> result in
> > >> +    reduced maximum throughput on that device and possibly on
> > >> + other
> > >> devices
> > >> +    assigned to that pmd thread. In the case such, a queue
> > >> + assignment is
> > >> made a
> > >> +    warning message will be logged: "There's no available
> > >> + (non-isolated)
> > >> pmd
> > >
> > > Above should read 'In the case where such a queue assignment is
> > > made, a
> > warning message will be logged'

[[BO'M]] 
Suggesting a simpler:
'If such a queue assignment is made a warning message ..."

> > >> +    thread on numa node N. Queue Q on port P will be assigned to
> > >> + the pmd
> > >> on
> > >> +    core C (numa node N'). Expect reduced performance."
> > >>
> > >>  - QEMU vCPU thread Affinity
> > >>
> > >> diff --git a/lib/dpif-netdev.c b/lib/dpif-netdev.c index
> > >> 4e29085..7557f32
> > >> 100644
> > >> --- a/lib/dpif-netdev.c
> > >> +++ b/lib/dpif-netdev.c
> > >> @@ -3195,6 +3195,23 @@ rr_numa_list_lookup(struct rr_numa_list *rr,
> > >> int
> > >> numa_id)
> > >>      return NULL;
> > >>  }
> > >>
> > >> +/* Returns next NUMA from rr list in round-robin fashion. Returns
> > >> +the first
> > >> + * NUMA node if 'NULL' or the last node passed, and 'NULL' if list
> > >> +is empty. */ static struct rr_numa * rr_numa_list_next(struct
> > >> +rr_numa_list *rr, const struct rr_numa *numa) {
> > >
> > > The comment above can be tidied up a little to better clarify the
> > behavior of this function.
> > > I ended up reading the comments for hmap_next() and hmap_first()
> > > before
> > it made sense, and even then it's a bit ambiguous, it ends up being
> > the code that explains the comments.
> > >
> > > You could clarify the following 2 statements:
> > >
> > > (1) "Returns the first NUMA node if 'NULL'" - If what is NULL? I
> > > assume
> > you mean the function parameter 'const struct rr_numa *numa' but it's
> > not clear on first reading.
> > >
> > > (2) " or the last node passed" - again this makes sense only when
> > > you
> > look into the behavior of the call 'hmap_next(&rr->numas, &numa-
> >node)'.
> > >
> > > You could say something like:
> > >
> > > "Attempt to return the next NUMA from a numa list in a round robin
> > fashion. Return the first NUMA node if the struct rr_numa *numa
> > argument passed to the function is NULL or if the numa node argument
> > passed to hmap_next is already the last node. Return NULL if the numa
> > list is empty."
> >
> > I'm not sure that references to implementation is a good way to write
> > comments (I mean 'passed to hmap_next' part).
> >
> > How about this:
> > """
> > /* Returns the next node in numa list following 'numa' in round-robin
> > fashion.
> >  * Returns first node if 'numa' is a null pointer or the last node in
> > 'rr'. */ """
> >
> > or
> >
> > """
> > /* The next node in numa list following 'numa' in round-robin fashion.
> >  * Returns:
> >  *     - 'NULL' if 'rr' is an empty numa list.
> >  *     - First node in 'rr' if 'numa' is a null pointer.
> >  *     - First node in 'rr' if 'numa' is the last node in 'rr'.
> >  *     - Otherwise, the next node in numa list following 'numa'. */
> > """
> >
> > ?
> 
> I'm happy with the first option you provided above, could you append
> returning NULL if the list is empty then I think we're good.
> 
> /* Returns the next node in numa list following 'numa' in round-robin
> fashion.
>  * Returns first node if 'numa' is a null pointer or the last node in 'rr'.
>  * Returns NULL if 'rr' numa list is empty. */

[[BO'M]] 
Sounds good to me. Anyone object to this wording? 

> 
> Thanks
> Ian
> >
> > >
> > >> +    struct hmap_node *node = NULL;
> > >> +
> > >> +    if (numa) {
> > >> +        node = hmap_next(&rr->numas, &numa->node);
> > >> +    }
> > >> +    if (!node) {
> > >> +        node = hmap_first(&rr->numas);
> > >> +    }
> > >> +
> > >> +    return (node) ? CONTAINER_OF(node, struct rr_numa, node) :
> > >> + NULL; }
> > >> +
> > >>  static void
> > >>  rr_numa_list_populate(struct dp_netdev *dp, struct rr_numa_list
> > >> *rr) { @@ -3249,6 +3266,7 @@ rxq_scheduling(struct dp_netdev *dp,
> > >> bool
> > >> pinned)
> > >> OVS_REQUIRES(dp->port_mutex)  {
> > >>      struct dp_netdev_port *port;
> > >>      struct rr_numa_list rr;
> > >> +    struct rr_numa *non_local_numa = NULL;
> > >>
> > >>      rr_numa_list_populate(dp, &rr);
> > >>
> > >> @@ -3281,11 +3299,28 @@ rxq_scheduling(struct dp_netdev *dp, bool
> > >> pinned)
> > >> OVS_REQUIRES(dp->port_mutex)
> > >>                  }
> > >>              } else if (!pinned && q->core_id == OVS_CORE_UNSPEC) {
> > >>                  if (!numa) {
> > >> -                    VLOG_WARN("There's no available (non isolated) pmd
> > >> thread "
> > >> +                    /* There are no pmds on the queue's local NUMA
> > node.
> > >> +                       Round-robin on the NUMA nodes that do have
> > pmds.
> > >> */
> > >> +                    non_local_numa = rr_numa_list_next(&rr,
> > >> non_local_numa);
> > >> +                    if (!non_local_numa) {
> > >> +                        VLOG_ERR("There is no available
> > >> + (non-isolated)
> > >> pmd "
> > >> +                                 "thread for port \'%s\' queue %d.
> > >> + This
> > >> queue "
> > >> +                                 "will not be polled. Is
> > >> + pmd-cpu-mask set
> > >> to "
> > >> +                                 "zero? Or are all PMDs isolated
> > >> + to other
> > >> "
> > >> +                                 "queues?", netdev_get_name(port-
> > >>> netdev),
> > >> +                                 qid);
> > >> +                        continue;
> > >> +                    }
> > >> +                    q->pmd = rr_numa_get_pmd(non_local_numa);
> > >> +                    VLOG_WARN("There's no available (non-isolated)
> > >> + pmd
> > >> thread "
> > >>                                "on numa node %d. Queue %d on port
> > \'%s\'
> > >> will "
> > >> -                              "not be polled.",
> > >> -                              numa_id, qid, netdev_get_name(port-
> > >>> netdev));
> > >> +                              "be assigned to the pmd on core %d "
> > >> +                              "(numa node %d). Expect reduced
> > >> performance.",
> > >> +                              numa_id, qid, netdev_get_name(port-
> > >>> netdev),
> > >> +                              q->pmd->core_id, q->pmd->numa_id);
> > >>                  } else {
> > >> +                    /* Assign queue to the next (round-robin) PMD
> > >> + on it's
> > >> local
> > >> +                       NUMA node. */
> > >>                      q->pmd = rr_numa_get_pmd(numa);
> > >>                  }
> > >>              }
> > >> --
> > >> 2.7.4
> > > This tested fine for me, tested with multiple rxqs distributed and
> > isolated over pmds on 2 different numa nodes with varying pmd masks.
> > Also passed sanity checks (clang, sparse compilation etc.).
> > >
> > > You can add the tested by tag for me but I'd like to see the changes
> > > for
> > the documentation and function comments above before acking.
> > >
> > > Tested-by: Ian Stokes <ian.stokes at intel.com>
> > >>
> > >> _______________________________________________
> > >> dev mailing list
> > >> dev at openvswitch.org
> > >> https://mail.openvswitch.org/mailman/listinfo/ovs-dev
> > >
> > >
> > >


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