On Fri, Feb 23, 2018 at 2:03 PM, Ben Pfaff <b...@ovn.org> wrote:
>
> ofproto_port_open_type() was surprisingly slow because it called the
> function ofproto_class_find__(), which itself was surprisingly slow
because
> it actually creates a set of strings and enumerates all of the available
> classes.
>
> This patch improves performance by eliminating the call to
> ofproto_class_find__() from ofproto_port_open_type().  In turn that
> required changing a parameter type and updating all the callers.
>
> Possibly it would be worth making ofproto_class_find__() itself faster,
> but it doesn't look like any of its other callers would be used in inner
> loops.
>
> A different patch that was also meant to speed this up reported the
> following performance improvements.  That patch just eliminated half of
the
> calls to ofproto_class_find__() in inner loops, whereas this one
eliminates
> all of them and should therefore perform even better.
>
>     This patch arises as a result of testing done by Ali Ginwala and Han
>     Zhou. Their test showed that commit 2d4beba resulted in slower
>     performance of ovs-vswitchd than was seen in previous versions of OVS.
>
>     With this patch, Ali retested and reported that this patch had nearly
>     the same effect on performance as reverting 2d4beba.
>
>     The test was to create 10000 logical switch ports using 20 farm nodes,
>     each running 50 HV sandboxes. "Base" in the tests below is OVS master
>     with Han Zhou's ovn-controller incremental processing patch applied.
>
>     base: Test completed in 8 hours
>     base with 2d4beba reverted: Test completed in 5 hours 28 minutes
>     base with this patch: Test completed in 5 hours 30 minutes
>
> Reported-by: Mark Michelson <mmich...@redhat.com>
> Signed-off-by: Ben Pfaff <b...@ovn.org>
> ---
>  ofproto/in-band.c |  2 +-
>  ofproto/ofproto.c | 30 ++++++++++--------------------
>  ofproto/ofproto.h |  2 +-
>  vswitchd/bridge.c | 12 ++++--------
>  4 files changed, 16 insertions(+), 30 deletions(-)
>
> diff --git a/ofproto/in-band.c b/ofproto/in-band.c
> index 849b1cedaff0..82d8dfa14774 100644
> --- a/ofproto/in-band.c
> +++ b/ofproto/in-band.c
> @@ -428,7 +428,7 @@ in_band_create(struct ofproto *ofproto, const char
*local_name,
>      struct in_band *in_band;
>      struct netdev *local_netdev;
>      int error;
> -    const char *type = ofproto_port_open_type(ofproto->type, "internal");
> +    const char *type = ofproto_port_open_type(ofproto, "internal");
>
>      *in_bandp = NULL;
>      error = netdev_open(local_name, type, &local_netdev);
> diff --git a/ofproto/ofproto.c b/ofproto/ofproto.c
> index f28bb896eee9..a982de9d8db4 100644
> --- a/ofproto/ofproto.c
> +++ b/ofproto/ofproto.c
> @@ -1966,27 +1966,18 @@ ofproto_port_dump_done(struct ofproto_port_dump
*dump)
>      return dump->error == EOF ? 0 : dump->error;
>  }
>
> -/* Returns the type to pass to netdev_open() when a datapath of type
> - * 'datapath_type' has a port of type 'port_type', for a few special
> - * cases when a netdev type differs from a port type.  For example, when
> - * using the userspace datapath, a port of type "internal" needs to be
> - * opened as "tap".
> +/* Returns the type to pass to netdev_open() when 'ofproto' has a port
of type
> + * 'port_type', for a few special cases when a netdev type differs from
a port
> + * type.  For example, when using the userspace datapath, a port of type
> + * "internal" needs to be opened as "tap".
>   *
>   * Returns either 'type' itself or a string literal, which must not be
>   * freed. */
>  const char *
> -ofproto_port_open_type(const char *datapath_type, const char *port_type)
> +ofproto_port_open_type(const struct ofproto *ofproto, const char
*port_type)
>  {
> -    const struct ofproto_class *class;
> -
> -    datapath_type = ofproto_normalize_type(datapath_type);
> -    class = ofproto_class_find__(datapath_type);
> -    if (!class) {
> -        return port_type;
> -    }
> -
> -    return (class->port_open_type
> -            ? class->port_open_type(datapath_type, port_type)
> +    return (ofproto->ofproto_class->port_open_type
> +            ? ofproto->ofproto_class->port_open_type(ofproto->type,
port_type)
>              : port_type);
>  }
>
> @@ -2728,10 +2719,9 @@ init_ports(struct ofproto *p)
>  static bool
>  ofport_is_internal_or_patch(const struct ofproto *p, const struct ofport
*port)
>  {
> -    return !strcmp(netdev_get_type(port->netdev),
> -                   ofproto_port_open_type(p->type, "internal")) ||
> -           !strcmp(netdev_get_type(port->netdev),
> -                   ofproto_port_open_type(p->type, "patch"));
> +    const char *netdev_type = netdev_get_type(port->netdev);
> +    return !strcmp(netdev_type, ofproto_port_open_type(p, "internal")) ||
> +           !strcmp(netdev_type, ofproto_port_open_type(p, "patch"));
>  }
>
>  /* If 'port' is internal or patch and if the user didn't explicitly
specify an
> diff --git a/ofproto/ofproto.h b/ofproto/ofproto.h
> index 1e48e1952aa2..8c85bbf7fb26 100644
> --- a/ofproto/ofproto.h
> +++ b/ofproto/ofproto.h
> @@ -290,7 +290,7 @@ int ofproto_port_dump_done(struct ofproto_port_dump
*);
>  #define OFPROTO_FLOW_LIMIT_DEFAULT 200000
>  #define OFPROTO_MAX_IDLE_DEFAULT 10000 /* ms */
>
> -const char *ofproto_port_open_type(const char *datapath_type,
> +const char *ofproto_port_open_type(const struct ofproto *,
>                                     const char *port_type);
>  int ofproto_port_add(struct ofproto *, struct netdev *, ofp_port_t
*ofp_portp);
>  int ofproto_port_del(struct ofproto *, ofp_port_t ofp_port);
> diff --git a/vswitchd/bridge.c b/vswitchd/bridge.c
> index cf9c79fd77cf..f03fb567f0be 100644
> --- a/vswitchd/bridge.c
> +++ b/vswitchd/bridge.c
> @@ -88,7 +88,6 @@ struct iface {
>
>      /* These members are valid only within bridge_reconfigure(). */
>      const char *type;           /* Usually same as cfg->type. */
> -    const char *netdev_type;    /* type that should be used for
netdev_open. */
>      const struct ovsrec_interface *cfg;
>  };
>
> @@ -822,7 +821,9 @@ bridge_delete_or_reconfigure_ports(struct bridge *br)
>              goto delete;
>          }
>
> -        if (strcmp(ofproto_port.type, iface->netdev_type)
> +        const char *netdev_type = ofproto_port_open_type(br->ofproto,
> +                                                         iface->type);
> +        if (strcmp(ofproto_port.type, netdev_type)
>              || netdev_set_config(iface->netdev, &iface->cfg->options,
NULL)) {
>              /* The interface is the wrong type or can't be configured.
>               * Delete it. */
> @@ -1778,7 +1779,7 @@ iface_do_create(const struct bridge *br,
>          goto error;
>      }
>
> -    type = ofproto_port_open_type(br->cfg->datapath_type,
> +    type = ofproto_port_open_type(br->ofproto,
>                                    iface_get_type(iface_cfg, br->cfg));
>      error = netdev_open(iface_cfg->name, type, &netdev);
>      if (error) {
> @@ -1856,8 +1857,6 @@ iface_create(struct bridge *br, const struct
ovsrec_interface *iface_cfg,
>      iface->ofp_port = ofp_port;
>      iface->netdev = netdev;
>      iface->type = iface_get_type(iface_cfg, br->cfg);
> -    iface->netdev_type = ofproto_port_open_type(br->cfg->datapath_type,
> -                                                iface->type);
>      iface->cfg = iface_cfg;
>      hmap_insert(&br->ifaces, &iface->ofp_port_node,
>                  hash_ofp_port(ofp_port));
> @@ -3445,13 +3444,10 @@ bridge_del_ports(struct bridge *br, const struct
shash *wanted_ports)
>              const struct ovsrec_interface *cfg = port_rec->interfaces[i];
>              struct iface *iface = iface_lookup(br, cfg->name);
>              const char *type = iface_get_type(cfg, br->cfg);
> -            const char *dp_type = br->cfg->datapath_type;
> -            const char *netdev_type = ofproto_port_open_type(dp_type,
type);
>
>              if (iface) {
>                  iface->cfg = cfg;
>                  iface->type = type;
> -                iface->netdev_type = netdev_type;
>              } else if (!strcmp(type, "null")) {
>                  VLOG_WARN_ONCE("%s: The null interface type is
deprecated and"
>                                 " may be removed in February 2013. Please
email"
> --
> 2.16.1
>
> _______________________________________________
> dev mailing list
> d...@openvswitch.org
> https://mail.openvswitch.org/mailman/listinfo/ovs-dev

I was debugging why ofproto_class_find__() was so slow in the scale testing
env, but not obvious slow down in a standalone setup when I just do repeat
port creation/deletion. It seems to be caused by acquiring the dpif_mutex
in dp_enumerate_types, but not sure what causes contention of that lock,
and why it is not a problem in the standalone environment.

This patch makes a lot more sense to me. And it should be even better than
reverting the patch "ofproto: Include patch ports in mtu overriden check",
because there was one call to ofproto_port_open_type() before that patch,
and with this patch there is none.

I suggest to update the commit message with new numbers from Ali's test.
Also, I suggest to include the original discussion in commit message for
more context to understand the impact:
https://mail.openvswitch.org/pipermail/ovs-discuss/2018-February/046140.html

Thanks,
Han
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